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Functional Inorganic Materials and Devices
Two-Step Approach for Conformal Chemical Vapor-Phase Deposition of Ultra-Thin Conductive Silver FilmsClick to copy article linkArticle link copied!
- Sabrina WackSabrina WackMaterials Research & Technology (MRT) Department, Luxembourg Institute of Science & Technology (LIST), L-4422 Belvaux, LuxembourgMore by Sabrina Wack
- Petru Lunca PopaPetru Lunca PopaMaterials Research & Technology (MRT) Department, Luxembourg Institute of Science & Technology (LIST), L-4422 Belvaux, LuxembourgMore by Petru Lunca Popa
- Noureddine AdjeroudNoureddine AdjeroudMaterials Research & Technology (MRT) Department, Luxembourg Institute of Science & Technology (LIST), L-4422 Belvaux, LuxembourgMore by Noureddine Adjeroud
- Christèle VergneChristèle VergneMaterials Research & Technology (MRT) Department, Luxembourg Institute of Science & Technology (LIST), L-4422 Belvaux, LuxembourgMore by Christèle Vergne
- Renaud Leturcq*Renaud Leturcq*Email: [email protected]Materials Research & Technology (MRT) Department, Luxembourg Institute of Science & Technology (LIST), L-4422 Belvaux, LuxembourgMore by Renaud Leturcq
Abstract
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Conductive ultra-thin silver films are commonly fabricated by physical vapor deposition methods such as evaporation or sputtering. The line-of-sight geometry of these techniques impedes the conformal growth on substrates with complex morphology. In order to overcome this issue, volume deposition technologies such as chemical vapor deposition or atomic layer deposition are usually preferred. However, the silver films fabricated using these methods are generally non-electrically conductive for thicknesses below 20–50 nm due to island formation. Here, we demonstrate a novel approach for producing ultra-thin conductive silver layers on complex substrates. Relying on chemical vapor-phase deposition and plasma post-treatment, this two-step technique allows the synthesis of highly conductive and uniform silver films with a critical thickness lower than 15 nm and a sheet resistance of 1.6 Ω/□ for a 40 nm-thin film, corresponding to a resistivity of 6.4 μΩ·cm. The high infrared reflectance further demonstrates the optical quality of the films, despite a still large root-mean-square roughness of 8.9 nm. We successfully demonstrate the highly conformal deposition in lateral structures with an aspect ratio of up to 100. This two-step deposition method could be extended to other metals and open new opportunities for depositing electrically conductive films in complex 3D structures.
Copyright © 2020 American Chemical Society
Introduction
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The deposition of highly uniform and conformal conductive ultra-thin films is of great interest in the microelectronics industry where the miniaturization of semiconductor devices introduces complex three-dimensional structures with a high aspect ratio (AR). (1,2) Consequently, one of the main challenges is to be able to uniformly fill the metallic films into these structures. Silver is of particular interest due to its low electrical resistivity, which is beneficial for microelectronic applications. (3−5) More generally, its outstanding optical properties make it a good choice for several applications including optical coatings for windows or lenses, (6) mirrors (7) or sensors, (8,9) while its chemical reactivity is used in antibacterial surfaces. (10) More and more of these applications require a conformal growth of ultra-thin silver layers, which represents a challenge for most deposition methods.
Silver films with the highest electrical conductivity and lowest critical thickness are currently produced by line-of-sight methods such as physical vapor deposition (PVD), (11−13) among which ultra-thin silver films with the best morphological and electrical properties are produced without the need of a seed layer by sputtering using Al and Cu doping. (14−16) Line-of-sight methods are however not suitable for complex 3D shapes (e.g., trenches) and present uniformity issues on nonflat substrates. Non-line-of-sight techniques such as chemical vapor deposition (CVD) and atomic layer deposition (ALD) often produce non-electrically conductive coatings for thickness below 20–50 nm. (2,17−21) Whether the synthesis is made by plasma-enhanced ALD (PE-ALD) or thermal ALD, the growth of the metallic film leads to a nanoparticle (NP) structure for low thickness. Nevertheless, several recent works have successfully demonstrated the reduction of the critical thickness, down to 22 nm for PE-ALD performed at a low temperature, (19) at which diffusion of silver on the surface is strongly reduced. Although PE-ALD usually gives a higher coverage with a lower critical thickness than thermal ALD, (18−21) a critical thickness down to 9 nm was recently reported by thermal ALD using tertiary butyl hydrazine as a coreactant. (22)
One major difficulty in producing ultra-thin continuous silver or other noble metals on oxide substrates is the formation of separated clusters due to the higher surface energy of metallic materials as compared to oxide surfaces. The deposition follows the Volmer–Weber growth mechanism and further leads to an NP morphology rather than a continuous layer. This has been demonstrated for Cu films (2,23−25) and for Ag films. (5,18,19,26) However, studies on the ALD of metal Ag are much less common than those of Cu since the exact deposition mechanism is not yet fully understood.
The reduction of the critical thickness of conductive films is one of the major research activity in the deposition of metal films, and several techniques have already been investigated, mainly for PVD methods (see refs (14) and (16) and references therein). The use of a wetting layer has demonstrated strong improvement for the growth of ultra-thin continuous metal films (see detailed review in refs (2) and (16)). Although good results were obtained in the case of line-of-sight techniques, (11−14,27−33) only noncontinuous films (34) or a slight enhancement of the coverage (5) were observed when chemical vapor-phase methods were engaged. A two-step approach consisting of the deposition of a metal-containing film subsequently reduced to a metallic state was proved for copper thin layers. (2,35) However, this will be difficult to transfer to silver coatings as stable Ag (II) complexes are extremely complex to obtain, mainly due to their more noble character as compared to Cu. At last, Al and Cu doping has demonstrated strong reduction of the Ag film roughness and critical thickness of films deposited by sputtering, (14−16) although a similar attempt has not yet been reported for ALD or CVD.
Here, we suggest a novel two-step approach for the conformal deposition of ultra-thin continuous metal coatings and demonstrate it on the synthesis of silver. The main part of this original method relies on the deposition of a thin film of compact metal nanoparticles using a forced pulsed CVD regime. This film, which is initially insulating, is further plasma treated in order to sinter the particles and create a quasi-continuous conducting coating, with resistivity and critical thickness close to the values obtained by PVD. (14,16) This ultra-thin silver layer shows a high conformality, even on a lateral structure with an aspect ratio of up to 100. The high-performances as an optical reflector on complex substrates are proven by a high infrared reflectance.
Experimental Section
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ALD Reactor and Film Growth
The experiments for the deposition of silver layers have been performed on a Beneq TFS200 system equipped with an open-boat hot source HS500 for the silver precursor and the remote plasma option (Ar/H2 plasma). Details about the reactor are reported elsewhere. (26) The chamber temperature, which is measured close to the reactor and is assumed to be representative of the sample, was kept between 120 and 150 °C. Both Ar, used as precursor carrier and process gas, and H2 gases used during the process are Alphagaz 1 and Arcal Prime, respectively, from Air Liquide. Their flows are controlled using mass flow controllers. The reactor pressure is about 3 mbar during the deposition process. The Ag(fod)(PEt3) precursor ((triethylphosphine(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate)silver(I), C16H25AgF7O2P, minimum 98% purity, Strem Chemicals) was loaded into an open quartz boat and heated at temperatures ranging from 100 to 150 °C using the HS500 precursor cell. The Ag precursor was continuously injected and not pulsed as for a standard PE-ALD process. The injection of the precursor was regulated by the process argon flow kept at 300 sccm. A remote capacitively coupled plasma (RF, 13.56 MHz), with glow discharges fed with a mix of hydrogen (20 sccm) and argon (300 sccm) ignited at 100 W for 3 s, is used as a reducing agent and followed by 10 s of purge time. The Ar/H2 mixture flows continuously to avoid deposition of the Ag precursor in the plasma head. The distance of the plasma ground electrode (grid electrode) to the substrate was kept at 4 cm.
The plasma post-treatment was performed in the same reactor using a continuous plasma with glow discharges fed with a mix of hydrogen (20 sccm) and argon (300 sccm) ignited typically between 100 and 150 W for 1 to 3 min.
For the optical films, aluminum-doped zinc oxide (AZO) was deposited at 150 °C in the same chamber using trimethylaluminum (TMA, Sigma-Aldrich, 97%), diethylzinc (DEZ, Sigma-Aldrich, ≥ 52% in weight of Zn), and water as precursors. The TMA versus DEZ pulse ratio was 1/30. For the deposition of zinc oxide, the pulse times were 150 and 200 ms for DEZ and water, respectively. For the deposition of aluminum oxide, the pulse times were 100 and 100 ms for TMA and water, respectively. After each pulse, the purge times were kept at 10s.
Imaging and Thickness Measurements
The films have been imaged using scanning electron microscopy (SEM) with an FEI Helios NanoLab 650 equipment. The effective thickness was determined by energy dispersive spectroscopy (EDS). For Ag films deposited on a silicon substrate, an Xmax 50 mm2 equipment from Oxford Instrument connected to the above-cited SEM was used, and the data were analyzed by means of INCA software. For Ag films deposited on a glass substrate, a Quanta 200 10 mm2 equipment from EDAX Inc. connected to an FEI Quanta FEG 200 SEM was used, and the data were analyzed via GENESIS software. The X-ray signal is measured with an electron energy of 10 keV with the sample perpendicular to the electron beam and with the X-ray detector at a take-off angle of 35°. The thickness determination follows the electron probe microanalysis (EPMA) method, (36) as already demonstrated for Ag thin films deposited by ALD. (19,26) We performed the extraction by comparing the values of the experimental k ratio of Ag LIII lines, i.e., the ratio between the X-ray intensity measured on the sample and the X-ray intensity of a reference bulk material of the same element, with the one obtained by Monte Carlo simulations, following the method described in refs (37) and (38). This method has demonstrated reliable thickness values as compared to Rutherford backscattering spectroscopy and quartz crystal microbalance within 5%, even for film thickness below 10 nm. (39,40) The Monte Carlo simulations were performed with the CASINO software (version 2.5.1), (41) using the Mott cross section obtained by interpolation, which has shown to be the most accurate for metal thin films, (39,42) the Casnati effective section ionization, and the Joy and Luo ionization potential (see ref (43)). We have assumed a uniform Ag film with the same density as the bulk, i.e., 10.5 g/cm3. The resulting value of the thickness, called EDS equivalent thickness, corresponds thus to the amount of material deposited on the surface. The error bars are linked to the non-uniformity of the deposition and determined by the variation of EDS thickness of close points at the same position, typically 1 nm, and by a systematic error of the method evaluated to be of maximum 5%. (40) For the PE-ALD process, it is also needed to add the film coverage uncertainty (7%) due to the nanoparticle morphology with a coverage less than 100% (see (26)).
Crystal Structure
The crystallographic structure has been studied by X-ray diffraction (XRD) using a Bruker D8 Discover diffractometer with a monochromatic Cu Kα radiation of 0.1542 nm in grazing incidence (GIXRD at 0.5°).
Elemental and Chemical Composition
The elemental and chemical composition of the samples was investigated by X-ray photoelectron spectroscopy (XPS) on a Kratos Axis Ultra DLD system equipped with a monochromatic Al Kα X-ray source (hν = 1486.7 eV) operating at 150 W. The etching was carried out with an Ar+ ion beam operating at 2 kV to remove surface contamination. High-resolution spectra were acquired on a surface analysis of 300 × 700 μm2 with a pass energy of 20 eV and a 0.05 eV step size.
Electrical Measurements
The sheet resistance of the films has been measured by using an in-line four-point-probe system (from Jandel) on Ag films deposited on 2 mm-thick glass substrates (Guardian Clear glass cut in dimensions 2.5 cm × 2.5 cm). The error bars were determined by the standard deviation of the values of sheet resistance measured at five different positions on the glass samples. The resistivity was calculated using the EDS thickness measured on the same glass substrate as we have observed variable growth rates on Si and on glass.
Optical Measurements
The optical properties (optical transmittance %T and optical reflectance %R) of the films deposited on glass have been measured on a Perkin Elmer Lambda 1050 spectrophotometer with a total absolute measurement system (TAMS) equipped with 49 mm integrating spheres and Si (UV–vis) and InGaAs (NIR) detectors. The absorbance %A of the film has been deduced from %T and %R using the relation %A = 100% – (%R + %T).
Conformality Measurements
We have used the microscopic lateral-high-aspect-ratio (LHAR) trenches from PillarHall technology (4th generation advanced LHAR4-series test chips). (44,45) The aspect ratio, which is the depth-to-width ratio, has been determined for the structure as the ratio of the lateral gap width (l) over the gap height (h of 500 nm).
rms Roughness
Atomic force microscopy (AFM) measurements were recorded in tapping mode using an AFM Innova from Bruker with a scanner 512 × 512 pixel resolution, and a 0.25 Hz scan rate was used to measure the surface roughness average Sq. The AFM scans were performed over 1 × 1 μm2 areas. Data treatment was performed with Gwyddion software.
Results and Discussion
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Principle and Morphological Properties
The suggested process is based on the PE-ALD of silver using Ag(fod)(PEt3) as the silver precursor and H2-based plasma as the reducing agent in conditions similar to the ones demonstrated for a standard PE-ALD regime. (19,26) In order to obtain a conducting ultra-thin film, the main challenge is to obtain a dense and compact deposit. Both standard ALD and CVD rely on the reaction of the precursor with the surface, leading to a nonconducting island morphology, due to the specific Volmer–Weber growth mechanism. Electrical conduction is achieved only after the coalescence, characterized usually by a high critical thickness. (5,18,19,26,46,47) In order to circumvent this morphology, we have used a modified processing condition in order to favor the gas-phase reaction before the surface reaction. This is usually avoided in the ALD or CVD of the thin film as it leads to a lack of control over the thickness and to deposition of nanoparticles. This regime has been referred to “pulsed-CVD”. (48,49)
This peculiar pulsed-CVD regime was achieved by continuously injecting the metal–organic silver precursor in the reactor while keeping the pulsed hydrogen-based plasma sequence from PE-ALD. The as-deposited film (Figure 1a) is made of compact silver-based nanoparticles with a surface coverage close to 100% that is usually not achieved at low thickness with CVD or ALD methods. The as-deposited film has a high sheet resistance (6 ± 5 MΩ/□ for the film in Figure 1a), which we attribute to the remaining precursor on the surface of the nanoparticles, as discussed below. This process leads to a typical growth rate of 0.30 ± 0.10 nm/min. In order to make the deposit conductive, a second step of post-treatment (PT) is performed, as already demonstrated for solution-processed Ag nanoparticles. (50,51) After a hydrogen-based plasma PT, the compact nanoparticles sinter and form a quasi-continuous ultra-thin silver film with a low sheet resistance (6 ± 1 Ω/□ for the film in Figure 1b). This decrease of the sheet resistance by six orders of magnitude is remarkable as previous reports for silver thin layers obtained by gas phase synthesis suggest that post-processing steps usually increase the sheet resistance of silver films due to the dewetting effect. (52) This difference might be attributed to the very peculiar morphology of the as-deposited film. The reduction of the sheet resistance was observed for PT time as low as 5 s, and no significant change was further observed up to 3 min in the conditions used here for flat substrates. The films have been deposited on different substrates including Si (with native oxide), glass, and ZnO- or AZO-coated Si and glass. The main observation is a lower deposition rate on a ZnO (or AZO)-coated substrate, but we did not observe any change of morphology both for as-deposited and post-treated films on all substrates.
Figure 1
Figure 1. Scanning electron micrographs of Ag thin films on glass substrates (a) as-deposited and (b) post-treated films. The EDS equivalent thickness is 24 ± 2 nm in both cases. The values shown in the middle of the images correspond to the sheet resistance of the Ag layer.
Figure 2
Figure 2. Morphological properties of Ag thin films. (a, b) Atomic force micrographs of Ag thin films on silicon substrates (a) as-deposited and (b) post-treated films. The EDS equivalent thickness is 40 ± 2 nm in both cases. The values shown in the middle of the images correspond to the rms roughness of the Ag layer. (c) SEM cross section of the as-deposited Ag thin film on a silicon substrate. The value shown in the middle of the image corresponds to the EDS equivalent thickness of the Ag layer.
The morphological properties of the Ag films have been investigated in Figure 2. A 40 nm-thick Ag as-deposited film presents a high rms roughness (Figure 2a), which is slightly reduced after plasma post-treatment but still remains important (Figure 2b). SEM cross-section has been performed on the Ag film deposited on the Si substrate, and, as seen in Figure 2c, it demonstrates that the film is rather composed of multiple layers of particles.
Chemical Composition and Crystallographic Properties
The chemical and crystallographic properties of the Ag films have been investigated in order to follow the evolution after deposition and after the post-treatment. Figure 3a,b presents the elemental composition of the Ag layer acquired before and after post-treatment, respectively, at different argon sputtering times (0, 140, and 280 s). For the as-deposited film (Figure 3a), the presence of usual contaminants (carbon and oxygen) on the surface of samples exposed to air is observed. Fluorine and phosphorus suggest the presence of unreacted precursors on the particle surface, which also leads to additional carbon and oxygen amounts and explains the high sheet resistance of the as-deposited film. Due to the small thickness of the film (26 ± 2 nm), the presence of Si could be attributed to the silicon and SiO2 from the substrate. The amount is however close to the detection limit of XPS, which is in line with the compact film morphology (Figure 1a). After 140 s of etching, one might observe the removal of surface contaminants and the unreacted precursor. The almost complete decomposition of the silver precursor is proven by the low amount of carbon, oxygen, fluorine, and phosphorus (last two elements are close to the limit of detection of XPS). The Ag atomic percentage is thus elevated. After 280 s, the interface between the silicon substrate and the deposit is reached since we observe that the Ag amount diminishes, whereas the silicon and oxygen amounts increase. After post-treatment (Figure 3b), the surface contaminants (carbon and oxygen) and the unreacted precursor (fluorine and phosphorus) observed before argon sputtering are still present. However, the fluorine content is strongly reduced as compared to the film before post-treatment. The high O amount on the surface might indicate partial oxidation of silver or the presence of OH groups at the surface as the film is exposed to air after post-treatment. The non-100%-covering film structure evidencing the presence of gaps (Figure 1b) and its small thickness (EDS equivalent thickness of 26 ± 2 nm) allow the detection of the silicon and SiO2 from the substrate. After 140 s of etching, the surface contaminants and the unreacted precursor are removed. Then, the film–substrate interface is reached.
Figure 3
Figure 3. (a, b) Elemental composition (in at.%) of Ag thin films synthetized on a silicon substrate using the new process (EDS equivalent thickness of 26 ± 2 nm) measured by XPS before (etching time, 0 s) and after Ar sputtering (two different etching times, 140 and 280 s). (a) As-deposited and (b) post-treated Ag thin films. (c) Modified Auger parameter (α′) of Ag for different etching times for as-deposited (red squares) and post-treated (black disks) layers. The blue line corresponds to a reference Ag foil. The error bars correspond to the experimental error linked to the spectrum acquisition step size. (d) X-ray diffraction spectrogram of Ag thin films synthetized on a silicon substrate (EDS equivalent thickness of 61 ± 3 nm) corresponding to as-deposited (in red) and post-treated (in black) films. The inset corresponds to the crystallite size extracted from (111), (200), (220), and (311) diffraction peaks of as-deposited (in red) and post-treated (in black) films.
By quantifying the value of the modified Auger parameter α′ (Figure 3c), the oxidation state of silver (53,54) can be determined. The low Auger parameter before sputtering is an indication of the remaining precursor for the as-deposited film or the oxidized silver surface for post-treated film. In the bulk (after 140 and 280 s of Ar etching), the as-deposited film is already made of metallic silver nanoparticles, even if it is non-electrically conductive, proving that a first reduction reaction occurred before the production of the particles. The plasma post-treatment slightly enhances the metallic nature of Ag, which, along with a lower amount of fluorine in the elemental analysis, highlights the removal of the unreacted precursor on the particle surface.
The XRD diffractogram (Figure 3d) shows that the as-deposited film already consists of polycrystalline face-centered cubic (fcc) silver (Fm3̅m) (JCPDS 04-0783) and exhibits (111), (200), (220), and (311) typical reflections. No signatures of other phases, such as silver oxide, are observed. The microscopic crystalline structure is slightly affected by the plasma post-treatment. Indeed, the main difference between the two products remains in the crystallite size as determined by the analysis of the peak width using a Lorentzian fitting function and the Debye–Scherrer equation, (55,56) which increases for the post-treated film (inset of Figure 3d), with a preferential growth in the (111) direction.
Electrical Properties
Owning its lowest bulk resistivity among the metals, Ag appears as a promising candidate for the replacement of aluminum or copper as interconnects in microelectronics. (3,4) The small-scale devices used here impose the synthesis of highly uniform and conformal conductive films with low critical thickness as a crucial criterion. The effect of the plasma post-treatment processing on the electrical properties of the silver layers was further investigated. The plot of the sheet resistance Rs as a function of the silver thickness is depicted in Figure 4.
Figure 4
Figure 4. Sheet resistance as a function of EDS equivalent thickness of Ag thin films on glass substrates. The data have been referred for the as-deposited (red triangle symbols) and post-treated (black square symbols) films. The blue spots have been obtained by a standard ALD process, following our previous work. (26) The green curve has been plotted as a reference for the Ag thin film deposited by magnetron sputtering, following the publication of Hauder et al. (3)
The as-deposited silver films (triangle symbols) present a very high sheet resistance, almost independent of the thickness. The PT strongly reduces this sheet resistance (square symbols), which becomes thickness dependent, as expected for a uniformly conductive film. The critical thickness (above which the deposits are conducting) is lower than 15 ± 1 nm, for which the sheet resistance reaches a value of 1.2 ± 0.1 kΩ/□ after post-treatment. This is very close to the state-of-the-art values for sputter-deposited thin films for the same thickness (green curve (3)) and well below the 63 ± 5 nm (value in gray circles) for the standard PE-ALD process using the same conditions as the one used in this work. (26) It is also lower than 22 nm, the lowest value for PE-ALD reported by Kariniemi et al. (19)
We have finally investigated the uniformity of the electrical properties of the coatings on a 10 cm × 10 cm flat glass substrate. An average value of the sheet resistance of 3.5 ± 1.4 Ω/□, i.e., with a standard deviation of 40% over the full sample, confirms the large-scale efficiency of the deposition performed in a standard non-optimized reactor with a diameter of 200 mm.
Optical Properties
We have further investigated the optical properties of the deposited silver films as ultra-thin Ag films can be used for optical coatings in windows, lenses, (6) or mirrors. (7) In order to investigate the functional properties of films synthesized using the new suggested process, we perform optical analysis of the as-deposited and post-treated Ag films.
The optical properties of a 42 ± 2 nm-thick Ag film deposited on a glass substrate are shown in Figure 5a. The as-deposited film composed of compact particles presents a strong and broad absorbance peak ranging from the visible to the NIR range, which is typical for a film of aggregated nanoparticles, where the plasmon resonance of small silver particles (58) is broadened by the strong dipolar interaction between particles. (59) The decrease in reflectance and increase in transmittance at a longer wavelength are due to the absence of long-range conduction. The reflectance strongly increases after PT and reaches up to 97% in the infrared region, while the transmittance and the absorbance are strongly reduced in the NIR region. This can be explained by the widened conduction paths (free electrons in metal layers) due to the quasi-continuous film morphology, thus confirming the good long-range electrical conduction properties obtained after PT. The absorbance of the post-treated film does not show any signature of aggregated nanoparticles that is the sign of a good sintering of the particles. The residual absorbance of the post-treated film in the visible region might be related to defects in the silver coatings, either due to holes or to the roughness of the deposit (rms roughness of 10.7 ± 0.2 nm for the as-deposited film and 8.9 ± 0.6 nm for the post-treated film (see Figure 2). The optical properties of a Ag layer of 15 ± 1 nm, i.e., close to the critical thickness, follow the same trend (Figure S1, Supporting information). Due to lower thickness of the Ag layer and presence of more gaps in the film morphology, the spectrum presents a lower reflectance and a high broadband absorbance, as already demonstrated for defective thin Ag films deposited by sputtering. (60)
Figure 5
Figure 5. Optical properties of Ag thin films on glass substrates and application as infrared-reflective (IRR) coating. (a) Transmittance (%T in solid lines), reflectance (%R in dashed lines), and calculated absorbance (%A = 100 – %R – %T in dash-dot lines) spectra as a function of light wavelength corresponding to the as-deposited (in red) and post-treated (in black) Ag thin layer. The EDS equivalent thickness is 42 ± 2 nm. (b) Picture of a bent glass substrate of 10 cm × 10 cm coated with a 45 nm (thickness determined by ellipsometry) AZO and targeted 40 nm Ag thin film. (c) Transmittance (%T in red) and reflectance (%R in blue) spectra as a function of light wavelength for an IRR stack based on a Ag thin layer (targeted thickness below 20 nm) embedded in the AZO matrix (45 nm for each layer). The inset represents a scheme of the multilayer stack. Plain lines correspond to the measured spectra, and dashed lines correspond to the calculated spectra using, for the Ag film, the optical constants represented in panel (d) and a thickness of 12 nm. (d) Real part (ε1) and imaginary part (ε2) of the dielectric constant used for modelling the silver film in the calculation in panel (c). The model used for simulating the experimental data (plain line) is compared to the optical constants for the evaporated Ag thin film determined by Johnson and Christy. (57) (e) Picture of the same kind of stack as panel (c) deposited on a two-sided-bent glass substrate of 10 cm × 10 cm. Glass thickness is 2 mm.
Infrared-reflective (IRR) coatings play an important role in the heat management of glazing products by avoiding heat to be transferred. (61) The ultra-thin silver film embedded in metal oxides has currently exhibited the highest performances. (62) As proof of principle, we have grown an ultra-thin silver layer (targeted thickness below 20 nm) using our novel approach between two AZO layers (thicknesses of 45 nm, see Figure 5c), the full stack being deposited in the same reactor, thus avoiding the influence of the environment. The resulting stack exhibits the typical wavelength dependence for an IRR coating, with a broad transmittance peak in the visible range and a high reflectance in the NIR range. (62) The transmittance and reflectance spectra have been simulated using a parametric model for the optical constant of the Ag thin film, and the optical constant was determined separately for the AZO films deposited by ALD. The best fit is obtained using a film thickness of 12 nm and the optical constants shown in Figure 5e. As compared to reference Ag films deposited by evaporation (dashed lines in Figure 5e), (57) the main difference is the higher imaginary part of the dielectric constant ε2 for the two-step process by a factor of two to three. In the free electron model, ε2 is proportional to the d.c. resistivity of the metal (see, e.g., ref (63)), thus this higher value is directly linked to the higher d.c. resistivity of our films as compared to more continuous films, as already shown in Figure 4. The additional peak observed below 500 nm can be explained by localized surface plasmon resonance due to morphological defects in the film.
The synthesis performed on a flat 10 cm × 10 cm glass substrate presents a good optical uniformity for both the reflective and IRR coatings, with a standard deviation of less than 20% on the optical transmittance and reflectance, the span being mostly due to the deposition gradient along the non-optimized 200 mm diameter reactor. At last, we prove in Figure 5b,e that the optical films can be uniformly formed on complex substrate shapes; here, a glass sample of 10 cm × 10 cm bent over two perpendicular directions, which is an important challenge for line-of-sight methods. The uniform silver coating is clearly visible on these pictures for the both kinds of stacks: the reflecting thick silver film in Figure 5b and the transparent IRR coating in Figure 5e.
Highly Conformal Deposition
At last, we investigate the conformality of the deposition, which is one of the major advantages of CVD methods as compared to PVD, with the possibility of covering 3D structures with high complexity (Figure 6a,b). For this purpose, we have investigated the conformal synthesis of Ag thin films on 3D structures with a lateral high aspect ratio (LHAR) from PillarHall technology. (1,44,45,64,65) Although ALD is the most promising technique for conformal deposition, the PE-ALD of the Ag thin film suffers from the recombination of plasma species (radicals) on the surfaces, which prevents the growth deeper into such a structure. (2,35)
Figure 6
Figure 6. Degree of conformality of Ag thin films on 3D structures. (a, b) Scheme of an expected thin film deposition on a lateral high aspect ratio structure by the (a) line-of-sight technique and (b) conformal technique. (c) Low-magnification SEM cross section of post-treated Ag thin films synthetized on an LHAR structure (AR of 100). (d, e) High-magnification SEM cross sections of the structure shown in panel (c), taken (d) at the entrance and (e) at the back of the LHAR structure. (f, g) SEM images of post-treated Ag thin films grown on the sidewalls of a micro via hole (zoomed in image in panel (g)). (h) SEM image of a Ag thin layer after PT deposited on silicon pillars.
We demonstrate in Figure 6c–e that we managed to produce Ag thin layers extremely conformal on top, bottom, and at the back of an LHAR with an aspect ratio of 100. As compared to this result, the standard PE-ALD method gives poor uniformity over LHAR trenches with no deposition on the back (Figure S2, Supporting Information). The morphology of the Ag continuous film on the sidewalls of a micro via hole is very uniform even in the lateral directions (Figure 6f,g), making the process a good candidate for conducting interconnects in microelectronics. (66) At last, we exhibit the conformal deposition on silicon pillars (Figure 6h), which is of interest for optical nanoantennas, (67) and due to the pillars’ high surface-to-volume ratios, applications as optical biosensing could be aimed. (68,69) The analysis of conformality has been performed on such a kind of structures (lateral, sidewall, or pillars) for mainly platinum-group metals, (64,70,71) but, to the best of our knowledge, this is the first time for Ag films since usually only vertical structures are studied. (72,73)
In order to quantify the degree of conformality, thickness profiles of the Ag film deposited into a “quasi-infinite trench” with a high AR of 10,000 (opening width w of 100 μm, lateral gap width l of 5000 μm, and gap height h of 500 nm) have been plotted to get rid of the depth effect (44) (Figure 7a). The thickness (determined by EDS) and the penetration depth have been measured after removing the top membrane of the LHAR structure (Figure S3, Supporting Information). The profiles show that the standard PE-ALD process follows an exponential decrease, t = Ae–x/B. This can be explained by the recombination of hydrogen radicals on the surfaces. (2) In contrast to this result, the Ag thin layer formed by the new approach follows the thin film solution of the diffusion law equation, t = Ae–x2/B, characterized by the presence of a plateau up to a penetration depth of 5 μm (AR = 10) followed by an exponential decrease. This behavior can be explained by deposition limited by the diffusion of precursors into the structure. (74)
Figure 7
Figure 7. (a) Thickness profiles measured on an LHAR structure with an AR of 10,000 (w of 100 μm, l of 5000 μm, and h of 500 nm) of Ag films deposited with the standard PE-ALD process (blue) and with our novel approach before (red) and after (black) plasma post-treatment. The thickness has been measured by EDS after removing the top membrane of the LHAR structure. The fits are an exponential dependence for the standard PE-ALD method and a diffusion law for the novel approach (see main text). (b–g) Scanning electron micrographs (top view) of Ag thin films (b–d) before and (e–g) after the post-treatment step and synthetized in the same structure as panel (a) at a penetration depth (PD) of (b–e) 0, (c–f) 9, and (d–g) 20 μm. The values on the middle of the images correspond to the EDS equivalent thickness of the Ag layer.
For both as-deposited and post-treated films, our novel approach gives a thickness variation of less than 10% for an AR of up to 12 and less than 50% for an AR of up to 40. This is four to five times larger than that measured for the standard PE-ALD method (10% variation for AR < 3 and 50% for AR < 8). The SEM images of Ag as-deposited and post-treated films in the LHAR are shown at different penetration depths in Figure 7b–g. We manage to deposit continuous Ag films deeply into the trench. The main morphological characteristics of the film, i.e., compact particles for the as-deposited film and the merged particles after the post-treatment, are both preserved deep into the structure, showing that both steps can be used efficiently in high aspect ratio structures. The layers remain continuous until a penetration depth of 9 μm, after which the thickness becomes lower than the critical thickness (see Figure 4), with film morphology becoming disconnected. This value covers largely the requirements of the current microelectronic applications. We point out that the plasma post-treatment seems to be more effective than the PE-ALD process in reaching structures with a large aspect ratio despite the fact that the plasma conditions are similar. This difference could be due to different doses used in the two processes since the post-treatment is applied once during a long time, while the PE-ALD process is using multiple short plasma pulses, which could allow a better diffusion of the plasma species into the trench. However, the involved mechanism and required species could also be very different in both processes. A deeper understanding of the chemical mechanisms occurring during both the deposition and the post-treatment could be very valuable in order to fully understand the large coverage obtained with the two-step process.
Conclusions
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In summary, a new deposition method for fabricating ultra-thin Ag conductive thin layers has been exposed. It is based on the chemical vapor-phase technique with a two-step approach: (1) formation of a compact film of silver-based nanoparticles by a plasma-enhanced process followed by (2) plasma post-treatment in order to sinter the particles. The plasma PT improves the electrical conductivity significantly, demonstrating a conductive 15 ± 1 nm-thin silver film synthetized by a chemical vapor-phase approach. A better unreacted-precursor removal and an enhancement of the metallic nature of polycrystalline Ag have also been proven after post-treatment. The high reflectance of up to 94% and the low absorbance of 3% in the infrared region for a silver thickness of 42 ± 2 nm justify the relevance of the product for high-performance IRR coatings. This novel approach allows a conformal deposition of 3D substrates that is a huge advantage as compared to line-of-sight techniques. This new processing approach opens a very promising path for the use of ultra-thin silver films for electronic and optoelectronic applications and could be extended to other metals deposited from metal–organic precursors.
Supporting Information
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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsami.0c08606.
Additional and complementary analyses (optical properties, degree of conformality, and penetration depth determination) (PDF)
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Author Information
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- Renaud Leturcq - Materials Research & Technology (MRT) Department, Luxembourg Institute of Science & Technology (LIST), L-4422 Belvaux, Luxembourg;
http://orcid.org/0000-0001-7115-9172;
- Sabrina Wack - Materials Research & Technology (MRT) Department, Luxembourg Institute of Science & Technology (LIST), L-4422 Belvaux, Luxembourg;http://orcid.org/0000-0002-7693-8746
Acknowledgments
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The authors acknowledge the support of Jean-Luc Biagi for the EDS measurements, and S.W. acknowledges the insightful discussions with Bianca Rita Pistillo.
References
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This article references 74 other publications.
- 1Cremers, V.; Puurunen, R. L.; Dendooven, J. Conformality in Atomic Layer Deposition: Current Status Overview of Analysis and Modelling. Appl. Phys. Rev. 2019, 6, 021302 DOI: 10.1063/1.5060967Google Scholar1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXht1CnurfN&md5=bbb6e90258bdc074511eee3fe6ec4478Conformality in atomic layer deposition: Current status overview of analysis and modellingCremers, Veronique; Puurunen, Riikka L.; Dendooven, JolienApplied Physics Reviews (2019), 6 (2), 021302/1-021302/43CODEN: APRPG5; ISSN:1931-9401. (American Institute of Physics)A review. Atomic layer deposition (ALD) relies on alternated, self-limiting reactions between gaseous reactants and an exposed solid surface to deposit highly conformal coatings with a thickness controlled at the submonolayer level. In this work, we aim to review the current status of knowledge about the conformality of ALD processes. We describe the basic concepts related to the conformality of ALD, including an overview of relevant gas transport regimes, definitions of exposure and sticking probability, and a distinction between different ALD growth types obsd. in high aspect ratio structures. The different types of high aspect ratio structures and characterization approaches that have been used for quantifying the conformality of ALD processes are reviewed. The different classes of models are discussed with special attention for the key assumptions typically used in the different modeling approaches. The influence of certain assumptions on simulated deposition thickness profiles is illustrated and discussed with the aim of shedding light on how deposition thickness profiles can provide insights into factors governing the surface chem. of ALD processes. We hope that this review can serve as a starting point and ref. work for new and expert researchers interested in the conformality of ALD and, at the same time, will trigger new research to further improve our understanding of this famous characteristic of ALD processes. (c) 2019 American Institute of Physics.
- 2Hagen, D. J.; Pemble, M. E.; Karppinen, M. Atomic Layer Deposition of Metals: Precursors and Film Growth. Appl. Phys. Rev. 2019, 6, 041309 DOI: 10.1063/1.5087759Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitFansr7O&md5=f3c610893e495981ef5668891380dd7eAtomic layer deposition of metals: Precursors and film growthHagen, D. J.; Pemble, M. E.; Karppinen, M.Applied Physics Reviews (2019), 6 (4), 041309/1-041309/63CODEN: APRPG5; ISSN:1931-9401. (American Institute of Physics)A review. The coating of complex three-dimensional structures with ultrathin metal films is of great interest for current tech. applications, particularly in microelectronics, as well as for basic research on, for example, photonics or spintronics. While at. layer deposition (ALD) has become a well-established fabrication method for thin oxide films on such geometries, attempts to develop ALD processes for elemental metal films have met with only mixed success. This can be understood by the lack of suitable precursors for many metals, the difficulty in reducing the metal cations to the metallic state, and the nature of metals as such, in particular their tendency to agglomerate to isolated islands. In this review, we will discuss these three challenges in detail for the example of Cu, for which ALD has been studied extensively due to its importance for microelectronic fabrication processes. Moreover, we give a comprehensive overview over metal ALD, ranging from a short summary of the early research on the ALD of the platinoid metals, which has meanwhile become an established technol., to very recent developments that target the ALD of electropos. metals. Finally, we discuss the most important applications of metal ALD. (c) 2019 American Institute of Physics.
- 3Hauder, M.; Gstöttner, J.; Hansch, W.; Schmitt-Landsiedel, D. Scaling Properties and Electromigration Resistance of Sputtered Ag Metallization Lines. Appl. Phys. Lett. 2001, 78, 838– 840, DOI: 10.1063/1.1345801Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXotlOktA%253D%253D&md5=4fded9be092b278a052ab1b662b3c327Scaling properties and electromigration resistance of sputtered Ag metallization linesHauder, M.; Gstottner, J.; Hansch, W.; Schmitt-Landsiedel, D.Applied Physics Letters (2001), 78 (6), 838-840CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Resistivity and electromigration were investigated for thin sputtered Ag films and microstructured Ag lines. Resistivities of thin films were found to be lower compared to copper and follow the prediction of the size effect. Microstructured Ag lines show a high electromigration resistance at accelerated stress measurements. Considering Joule heating of the lines, the activation energy for electromigration was found to be 0.58 eV. The extrapolated median lifetime of Ag lines was found to be similar or higher than for Cu lines.
- 4Gao, L.; Härter, P.; Linsmeier, C.; Gstöttner, J.; Emling, R.; Schmitt-Landsiedel, D. Metalorganic Chemical Vapor Deposition of Silver Thin Films for Future Interconnects by Direct Liquid Injection System. Mater. Sci. Semicond. Process. 2004, 7, 331– 335, DOI: 10.1016/j.mssp.2004.09.128Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXpvVelu70%253D&md5=463e309fc00d9f32b365958f21337089Metalorganic chemical vapor deposition of silver thin films for future interconnects by direct liquid injection systemGao, L.; Haerter, P.; Linsmeier, Ch.; Gstoettner, J.; Emling, R.; Schmitt-Landsiedel, D.Materials Science in Semiconductor Processing (2004), 7 (4-6), 331-335CODEN: MSSPFQ; ISSN:1369-8001. (Elsevier Ltd.)Deposition of Ag films by direct liq. injection-metal org. chem. vapor deposition (DLI-MOCVD) was chosen because this prepn. method allows precise control of precursor flow and prevents early decompn. of the precursor as compared to the bubbler-delivery. Silver(I)-2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionato-triethylphosphine [Ag(fod)(PEt3)] as the precursor for Ag CVD was studied, which is liq. at 30°C. Ag films were grown on different substrates of SiO2/Si and TiN/Si. Argon and nitrogen/hydrogen carrier gas was used in a cold wall reactor at a pressure of 50-500 Pa with deposition temp. ranging between 220°C and 350°C. Ag films deposited on a TiN/Si diffusion barrier layer have favorable properties over films deposited on SiO2/Si substrate. At lower temp. (220°C), film growth is essentially reaction-limited on SiO2 substrate. Significant dependence of the surface morphol. on the deposition conditions exists in our expts. According to XPS anal. pure Ag films are deposited by DLI-MOCVD at 250°C by using argon as carrier gas.
- 5Amusan, A. A.; Kalkofen, B.; Gargouri, H.; Wandel, K.; Pinnow, C.; Lisker, M.; Burte, E. P. Ag Films Grown by Remote Plasma Enhanced Atomic Layer Deposition on Different Substrates. J. Vac. Sci. Technol., A 2016, 34, 01A126 DOI: 10.1116/1.4936221Google ScholarThere is no corresponding record for this reference.
- 6Szczyrbowski, J.; Dietrich, A.; Hartig, K. Evaluation and Control of the Properties of Thin Sputtered Silver Films for Spectrally Selective Coatings. Sol. Energy Mater. 1987, 16, 103– 111, DOI: 10.1016/0165-1633(87)90012-8Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXlt1entbk%253D&md5=3fc15fc1f13ff268f769c2d8b9e8092dEvaluation and control of the properties of thin sputtered silver films for spectrally selective coatingsSzczyrbowski, J.; Dietrich, A.; Hartig, K.Solar Energy Materials (1987), 16 (1-3), 103-11CODEN: SOEMDH; ISSN:0165-1633.The influence of the deposition parameters on the elec. and optical properties of very thin Ag films prepd. by magnetron sputtering was studied. To evaluate the film properties, a method was used, which is based on simple optical transmission measurements. The results show that the specific resistivity, the plasma energy and the optical resistivity of films below 30 nm thickness are very sensitive to such deposition parameters as cathode power d. The variations in the optical and elec. properties are related to the d. of the sputtered films.
- 7Boccas, M.; Vucina, T.; Araya, C.; Vera, E.; Ahhee, C. Protected-Silver Coatings for the 8-m Gemini Telescope Mirrors. Thin Solid Films 2006, 502, 275– 280, DOI: 10.1016/j.tsf.2005.07.295Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XhslyjtLc%253D&md5=bcc72bb685f711f7fa9ec2f68561788aProtected-silver coatings for the 8-m Gemini telescope mirrorsBoccas, M.; Vucina, T.; Araya, C.; Vera, E.; Ahhee, C.Thin Solid Films (2006), 502 (1-2), 275-280CODEN: THSFAP; ISSN:0040-6090. (Elsevier B.V.)The twin 8-m diam. Gemini telescopes were designed to use silver-based coatings on the mirrors in order to provide very high reflectivity and ultra-low emissivity for optimal IR performance. A feasibility study provided both techniques and recipes to apply these thin films, and showed that a reflectivity of 99.1% at 10 μm was achievable. We have now produced bare and protected silver sputtered films in our coating plants and conducted environmental testing, both accelerated and in real-life conditions, to assess the durability in an observatory environment. We have also already applied, for the first time ever, protected-silver coatings on the main optical elements of a large telescope. We report here the performance of the films, the challenges to coat a 50 m2 primary mirror (M1) and our plans for coating maintenance.
- 8Butler, M. A.; Ricco, A. J. Chemisorption-Induced Reflectivity Changes in Optically Thin Silver Films. Appl. Phys. Lett. 1988, 53, 1471, DOI: 10.1063/1.100464Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1cXmtlOku7g%253D&md5=c8be4378ce03f5d8a48b7615b2d7357eChemisorption-induced reflectivity changes in optically thin silver filmsButler, M. A.; Ricco, A. J.Applied Physics Letters (1988), 53 (16), 1471-3CODEN: APPLAB; ISSN:0003-6951.The reflectivity of an optically thin metal film was used to investigate its interactions with chemisorbed mols. Reflectivity decreases for semitransparent, thin (50-250 Å) Ag films vacuum evapd. on the end of multimode optical fibers were obsd. at 860 nm during chemisorption of various mols. The magnitude of the decrease depends on the nature of the mol./Ag interaction. The dependence of this effect on film thickness is consistent with changes in the optical thickness as a result of chemisorption. This effect may lead to the development of new chem. sensors.
- 9Guo, S.; Wang, E. Noble Metal Nanomaterials: Controllable Synthesis and Application in Fuel Cells and Analytical Sensors. Nano Today 2011, 6, 240– 264, DOI: 10.1016/j.nantod.2011.04.007Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpvVWqtbg%253D&md5=f2f1f12222c748f2c2c07f311ae54411Noble metal nanomaterials: controllable synthesis and application in fuel cells and analytical sensorsGuo, Shaojun; Wang, ErkangNano Today (2011), 6 (3), 240-264CODEN: NTAOCG; ISSN:1748-0132. (Elsevier Ltd.)A review. Nobel metal nanomaterials (NMNs) with interesting phys. and chem. properties are ideal building blocks for engineering and tailoring nanoscale structures for specific technol. applications. Particularly, effectively controlling the size, shape, architecture, compn., hybrid and microstructure of NMNs plays an important role on revealing their new or enhanced functions and application potentials such as fuel cell and anal. sensors. This review article focuses on recent advances on controllable synthesis and fuel cell and sensing applications of NMNs. First, recent contributions on developing a wet-chem. approach for the controllable synthesis of noble metal nanomaterials with a rich variety of shapes, e.g. single-component Pt, Pd, Ag and Au nanomaterials, multi-component core/shell, intermetallic or alloyed nanomaterials, metal fluorescent nanoclusters and metal nanoparticles-based hybrid nanomaterials, are summarized. Then diversified approaches to different types of NMNs-based nanoelectrocatalysts with the aim to enhance their activity and durability for fuel cell reactions are outlined. The review next introduces some exciting push in the use of NMNs as enhanced materials or reporters or labels for developing new anal. sensors including electrochem., colorimetric and fluorescent sensors. Finally, we conclude with a look at the future challenges and prospects of the development of NMNs.
- 10Piedade, A. P.; Vieira, M. T.; Martins, A.; Silva, F. In Vitro Behaviour of Nanocrystalline Silver-Sputtered Thin Films. Nanotechnology 2007, 18, 105103, DOI: 10.1088/0957-4484/18/10/105103Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkvFSitLc%253D&md5=fdf78c354ded761fa9a961a5523bb169In vitro behaviour of nanocrystalline silver-sputtered thin filmsPiedade, A. P.; Vieira, M. T.; Martins, A.; Silva, F.Nanotechnology (2007), 18 (10), 105103/1-105103/5CODEN: NNOTER; ISSN:0957-4484. (Institute of Physics Publishing)Silver thin films were deposited with different preferential orientations and special attention was paid to the bioreactivity of the surfaces. The study was essentially focused on the evaluation of the films by x-ray diffraction (XRD), at. force microscopy (AFM), high-resoln. transmission electron microscopy (HRTEM), electron probe microanal. (EPMA) and contact angle measurements. The deposited thin films were characterized before and after immersion in S-enriched simulated human plasma to est. the influence of the preferential crystallog. orientation on the in vitro behavior. Silver thin films with and without (111) preferential crystallog. orientation were deposited by r.f. magnetron sputtering to yield nanocryst. coatings, high compact structures, very hydrophobic surfaces and low roughness. These properties reduce the chemisorption of reactive species onto the film surface. The in vitro tests indicate that silver thin films can be used as coatings for biomaterials applications.
- 11Guske, J. T.; Brown, J.; Welsh, A.; Franzen, S. Infrared Surface Plasmon Resonance of AZO-Ag-AZO Sandwich Thin Films. Opt. Express 2012, 20, 23215– 23226, DOI: 10.1364/OE.20.023215Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsFCisLfE&md5=2fce4f2e2b91798937f8876ada3a8923Infrared surface plasmon resonance of AZO-Ag-AZO sandwich thin filmsGuske, Joshua T.; Brown, Jeff; Welsh, Alex; Franzen, StefanOptics Express (2012), 20 (21), 23215-23226CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)Near-IR surface plasmon resonance (SPR) spectra were collected of thin multilayer films of aluminum-doped zinc oxide (AZO)/silver (Ag)/AZO on BK-7 glass in the Kretschmann configuration in air, with the silver layer thickness varying from 5 nm to 50 nm. The SPR results were interpreted by modeling the reflectance with a five-layer transfer-matrix method, with the aid of a simplex algorithm. The model indicated that the Ag plasma frequency was significantly higher than the bulk value, possibly due to Schottky effect charge transfer from the AZO to the Ag layer. Continuous silver films were made as thin as 10 nm, indicating an inhibition of metal island formation for Ag deposited on AZO.
- 12West, G. T.; Kelly, P. J.; Bradley, J. W. A Comparison of Thin Silver Films Grown Onto Zinc Oxide via Conventional Magnetron Sputtering and HiPIMS Deposition. IEEE Trans. Plasma Sci. 2010, 38, 3057– 3061, DOI: 10.1109/TPS.2010.2066580Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhs1WrsbfP&md5=552ae82c7daa8bcb02369b47dc5586bdA comparison of thin silver films grown onto zinc oxide via conventional magnetron sputtering and HiPIMS depositionWest, G. T.; Kelly, P. J.; Bradley, J. W.IEEE Transactions on Plasma Science (2010), 38 (11, Pt. 1), 3057-3061CODEN: ITPSBD; ISSN:0093-3813. (Institute of Electrical and Electronics Engineers)Silver coatings are commonly deposited via dc magnetron sputtering for use in a variety of applications that require high transparency to visible light and good elec. cond., including, for example, low-emissivity coatings. The films need to be fully dense in order to achieve the correct optical and elec. properties, although the typical growth mechanism for silver films is by the nucleation and coalescence of islandlike structures that can result in the generation of voids within the coating and uneven surface topog. As a consequence, in order to achieve acceptable elec. properties, the optical transparency of the silver coating is often compromised due to the excessive film thicknesses required for continuous elec. conductive layers. Conventional methods used to enhance the adatom mobility, hence increasing the d. of the coatings, include the application of an elec. bias to the substrate or substrate heating, both of which can be problematic for large-area dielec. substrates such as float glass or polymer web. One alternative is the prodn. of a coating using a deposition flux with a high fraction of ionization. This can be achieved via high-power impulse magnetron sputtering (HiPIMS), leading to an enhanced delivery of energy to the adatoms via recombination at the substrate surface. Thin films of silver were deposited onto zinc oxide-coated glass substrates via continuous dc and pulsed-dc magnetron sputtering and also via HiPIMS at the same time-averaged power in order to compare the structure and growth mechanisms via techniques, including AFM, XRD, and Hall-effect measurements for the elec. characterization.
- 13Banzai, K.; Naka, S.; Okada, H. MoO3/Ag/MoO3 Anode for Organic Light-Emitting Diodes and its Carrier Injection Property. Jpn. J. Appl. Phys. 2015, 54, 054101 DOI: 10.7567/JJAP.54.054101Google ScholarThere is no corresponding record for this reference.
- 14Gu, D.; Zhang, C.; Wu, Y.-K.; Guo, L. J. Ultrasmooth and Thermally Stable Silver-Based Thin Films with Subnanometer Roughness by Aluminum Doping. ACS Nano 2014, 8, 10343– 10351, DOI: 10.1021/nn503577cGoogle Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFamsL7E&md5=a8b714c4bec79c15b6d5dfc1ad5289bcUltrasmooth and thermally stable silver-based thin films with subnanometer roughness by aluminum dopingGu, Deen; Zhang, Cheng; Wu, Yi-Kuei; Guo, L. JayACS Nano (2014), 8 (10), 10343-10351CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Rough surface and poor stability of ultrathin Ag films limit their applications in nanophotonic and optoelectronic devices. Here, we report an approach for fabricating ultrasmooth and thermally stable Ag-based thin films on SiO2/Si substrates by Al-doping. The effect of Al-doping on the surface morphol. and stability of ultrathin Ag films at room temp. and elevated temp. was investigated. The 15 nm Al-doped Ag films with an Al at. concn. of 4% have a root-mean-square roughness as low as 0.4 nm. The smooth surface morphol. is maintained even after 300°C annealing in N2. Al-doping enhances the nuclei d. of films. Moreover, a capping layer spontaneously formed over the Al-doped Ag films restrains the surface diffusion and mass transportation of Ag atoms. Therefore, Al-doping induces ultrathin Ag films with highly stable and ultrasmooth surface morphol.
- 15Huang, J.; Liu, X.; Lu, Y.; Zhou, Y.; Xu, J.; Li, J.; Wang, H.; Fang, J.; Yang, Y.; Wang, W.; Tan, R.; Song, W. Seed-Layer-Free Growth of Ultra-Thin Ag Transparent Conductive Films Imparts Flexibility to Polymer Solar Cells. Sol. Energy Mater. Sol. Cells 2018, 184, 73– 81, DOI: 10.1016/j.solmat.2018.04.002Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXptlSht7Y%253D&md5=215222b18dae9a90dd2b355b7a386271Seed-layer-free growth of ultra-thin Ag transparent conductive films imparts flexibility to polymer solar cellsHuang, Jinhua; Liu, Xiaohui; Lu, Yuehui; Zhou, Yuhong; Xu, Junjun; Li, Jia; Wang, Haiqiao; Fang, Junfeng; Yang, Ye; Wang, Weiyan; Tan, Ruiqin; Song, WeijieSolar Energy Materials & Solar Cells (2018), 184 (), 73-81CODEN: SEMCEQ; ISSN:0927-0248. (Elsevier B.V.)In this work, by introducing Cu dopant, ultra-thin Ag transparent conductive films were prepd. on glass and PET substrates without seed layers. The percolation threshold thickness for the Cu doped Ag thin films was as low as 6nm with a RMS roughness only 0.19nm. The prepd. 6nm Cu doped Ag thin films, Ag(Cu), had a transmittance of 80% at 550nm and a sheet resistance of 14.1Ωsq-1. The Ag(Cu) thin films revealed excellent thermal, chem., and mech. stability. Flexible polymer solar cells using the Ag(Cu) electrode reached a convert efficiency of 7.53% with a very thin PTB7-Th:PC71BM active layer. The proposed ultra-thin alloy transparent conductive films are ease of fabrication and beneficial to light harvesting, which are promising for large-area applications in flexible photovoltaics.
- 16Yang, Y.; Song, W.; Ding, L. Dielectric/Ultrathin Metal/Dielectric Structured Transparent Conducting Films for Flexible Electronics. Sci. Bull. 2020, 1324, DOI: 10.1016/j.scib.2020.04.024Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhsFSisrfJ&md5=da3d2c95c075ada8187dd78e3f884934Dielectric/ultrathin metal/dielectric structured transparent conducting films for flexible electronicsYang, Ye; Song, Weijie; Ding, LimingScience Bulletin (2020), 65 (16), 1324-1326CODEN: SBCUA5; ISSN:2095-9281. (Elsevier B.V.)To be compatible with future new flexible electronics. The dielec./ultrathin metal/dielec. structured with long-term chem. stability, controllable surface chem. state (e.g., hydrophobic or hydrophilic)and adjustable work function and its more sophisticated integration in device should be further developed.
- 17Bahlawane, N.; Premkumar, P. A.; Brechling, A.; Reiss, G.; Kohse-Höinghaus, K. Alcohol-Assisted CVD of Silver Using Commercially Available Precursors. Chem. Vap. Deposition 2007, 13, 401– 407, DOI: 10.1002/cvde.200706610Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtVWnu77P&md5=b1cf7632c9c9530260660aa35616ece1Alcohol-assisted CVD of silver using commercially available precursorsBahlawane, Naoufal; Premkumar, Peter Antony; Brechling, Armin; Reiss, Guenter; Kohse-Hoeinghaus, KatharinaChemical Vapor Deposition (2007), 13 (8), 401-407CODEN: CVDEFX; ISSN:0948-1907. (Wiley-VCH Verlag GmbH & Co. KGaA)A novel chem. approach was demonstrated for the growth of high-quality, Ag films by CVD. This concept relies on the catalytic reactivity of cationic Ag, and of Ag surfaces with alcs. This leads to high-purity films using either state-of-the-art precursors or Ag salts that were not yet considered as CVD precursors. The occurrence of the catalytic oxidative-dehydrogenation of alcs., considered as the driving force in this process, was shown by in-situ mass spectrometry (MS). Films of fcc.-Ag with ρ ≤ 2 μΩ cm were grown without any noticeable contamination. Ag(hfac)COD leads to the growth of a (111) highly orientated film on glass at a rate of 1.66 nm min-1, while polycryst. films are grown at a rate of 18.5 nm min-1 using AgNO3.
- 18Niskanen, A.; Hatanpää, T.; Arstila, K.; Leskelä, M.; Ritala, M. Radical-Enhanced Atomic Layer Deposition of Silver Thin Films Using Phosphine-Adducted Silver Carboxylates. Chem. Vap. Deposition 2007, 13, 408– 413, DOI: 10.1002/cvde.200606519Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtVWnu77I&md5=171fe4da4eb1ffe070cdb7a6ec3e3e5aRadical-enhanced atomic layer deposition of silver thin films using phosphine-adducted silver carboxylatesNiskanen, Antti; Hatanpaa, Timo; Arstila, Kai; Leskela, Markku; Ritala, MikkoChemical Vapor Deposition (2007), 13 (8), 408-413CODEN: CVDEFX; ISSN:0948-1907. (Wiley-VCH Verlag GmbH & Co. KGaA)Silver films were deposited by radical-enhanced at. layer deposition using (2,2-dimethylpropionato)silver(I)triethylphosphine and hydrogen radicals. The silver precursor used is synthesized inhouse and characterized by using CHN elemental anal., IR spectroscopy, NMR, mass spectrometry and thermogravimetric anal./single DTA. The crystal structure of Ag(O2CtBu)(PEt3) is also solved. Trimeric units are revealed as the building blocks. The hydrogen radicals are produced by dissocg. mol. hydrogen with a microwave plasma discharge. The evapn. temp. of the silver precursor is 125°, and the film deposition temp. is 140°. The deposition is successful on glass and silicon, and the films are conformal. The satd. growth rate is 0.12 nm per cycle, with a 3 s silver precursor pulse and 5 s hydrogen radical pulse time. The overall cycle time is 14 s. The films are polycryst. and are visually mirror-like. The films contain 10 oxygen, 4.0 phosphorous, 1.0 carbon and 5.0 at.% hydrogen as impurities. Nevertheless, the films exhibit low elec. resistivity of only 6 μΩ-cm for a 40 nm thick film.
- 19Kariniemi, M.; Niinistö, J.; Hatanpää, T.; Kemell, M.; Sajavaara, T.; Ritala, M.; Leskelä, M. Plasma-Enhanced Atomic Layer Deposition of Silver Thin Films. Chem. Mater. 2011, 23, 2901– 2907, DOI: 10.1021/cm200402jGoogle Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXlvFClsLc%253D&md5=33e1707648ad5ee7d56f22e3456c1a4cPlasma-Enhanced Atomic Layer Deposition of Silver Thin FilmsKariniemi, Maarit; Niinisto, Jaakko; Hatanpaa, Timo; Kemell, Marianna; Sajavaara, Timo; Ritala, Mikko; Leskela, MarkkuChemistry of Materials (2011), 23 (11), 2901-2907CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)Thermal properties of various silver precursors known in the literature were evaluated in order to discover which precursor is the most suitable one for plasma-enhanced at. layer deposition (PEALD) of silver thin films. Ag(fod)(PEt3) (fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluorooctane-3,5-dionato) was found to be the best choice. Using Ag(fod)(PEt3) together with plasma-activated hydrogen, Ag thin films were deposited at growth temps. of 120-150°, and ALD-type saturative growth was achieved at 120-140°. At 120°, the growth rate was 0.03 nm per cycle. The plasma exposure time had also an effect on the growth rate: with shorter exposure times, the growth rate was lower over the whole deposition area. The films deposited at 120° contained relatively small amts. of impurities, but these still affected the elec. properties of the films. The resistivities were relatively low: about 20 nm thick films had a resistivity of 6-8 μΩ-cm. The morphol. and the crystal structure of the films were analyzed as well.
- 20Chalker, P. R.; Romani, S.; Marshall, P. A.; Rosseinsky, M. J.; Rushworth, S.; Williams, P. A. Liquid Injection Atomic Layer Deposition of Silver Nanoparticles. Nanotechnology 2010, 21, 405602, DOI: 10.1088/0957-4484/21/40/405602Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsVygt7bO&md5=6fa609726efa7e0deb45646abf356103Liquid injection atomic layer deposition of silver nanoparticlesChalker, P. R.; Romani, S.; Marshall, P. A.; Rosseinsky, M. J.; Rushworth, S.; Williams, P. A.Nanotechnology (2010), 21 (40), 405602/1-405602/7CODEN: NNOTER; ISSN:1361-6528. (Institute of Physics Publishing)Silver nanoparticles are being developed for applications in plasmonics, catalysts and anal. methods, amongst others. Herein, we demonstrate the growth of silver nanoparticles using an at. layer deposition (ALD) process for the first time. The silver was deposited from pulses of the organometallic precursor (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I) (1,5-cyclooctadiene)) dissolved in a 0.1 M toluene soln. Catalytic oxidative dehydrogenation of the silver was achieved using intermittent pulses of propanol. The effect of substrate temp. on the size and distribution of nanoparticles has been investigated over the temp. range 110-150 °C.Transmission electron microscopy reveals that the nanoparticles consist of fcc., facetted silver crystallites. The localized surface plasmon modes of the nanoparticles have been investigated using electron energy loss spectroscopy mapping. The distributions of plasmons within the ALD nanoparticles are comparable to those grown by soln. methods. Both dipolar and quadrupolar resonant modes are obsd., which is consistent with previous discrete dipole approxn. models. Energy loss mapping of a loss feature at 8.1 eV reveals that it correlates with the bulk or vol. region of the silver nanoparticles investigated here.
- 21Mäkelä, M.; Hatanpää, T.; Mizohata, K.; Meinander, K.; Niinistö, J.; Räisänen, J.; Ritala, M.; Leskelä, M. Studies on Thermal Atomic Layer Deposition of Silver Thin Films. Chem. Mater. 2017, 29, 2040– 2045, DOI: 10.1021/acs.chemmater.6b04029Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjtlCguro%253D&md5=a8e85af73ebb2debeea38bd15e5e5214Studies on Thermal Atomic Layer Deposition of Silver Thin FilmsMakela, Maarit; Hatanpaa, Timo; Mizohata, Kenichiro; Meinander, Kristoffer; Niinisto, Jaakko; Raisanen, Jyrki; Ritala, Mikko; Leskela, MarkkuChemistry of Materials (2017), 29 (5), 2040-2045CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)The growth of Ag thin films by thermal at. layer deposition (ALD) was studied. A com. Ag compd., Ag(fod) (PEt3), was applied with a reducing agent, di-Me amineborane (BH3(NHMe2)). A growth rate of 0.3 Å/cycle was measured for Ag at a deposition temp. of 110 °C. The purity of the particulate, polycryst. Ag thin films was studied with time-of-flight elastic recoil detection anal. (TOF-ERDA) and XPS. TOF-ERDA showed only small amts. of impurities in the film deposited at 110 °C, the main impurities being oxygen (1.6 at. %), hydrogen (0.8 at. %) and carbon (0.7 at. %). In addn. to the conventional ALD process, the idea of activation of the amineborate inside the ALD reactor was tested. A catalytic Ru surface was utilized to convert BH3(NHMe2) into possibly even more reducing species inside the reactor without contaminating the catalysts with a growing film.
- 22Golrokhi, Z.; Marshall, P. A.; Romani, S.; Rushworth, S.; Chalker, P. R.; Potter, R. J. The Influence of Tertiary Butyl Hydrazine as a Co-Reactant on the Atomic Layer Deposition of Silver. Appl. Surf. Sci. 2017, 399, 123– 131, DOI: 10.1016/j.apsusc.2016.11.192Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFent7fJ&md5=a7633b2983d86db735de36600bee22b8The influence of tertiary butyl hydrazine as a co-reactant on the atomic layer deposition of silverGolrokhi, Zahra; Marshall, Paul A.; Romani, Simon; Rushworth, Simon; Chalker, Paul R.; Potter, Richard J.Applied Surface Science (2017), 399 (), 123-131CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)Ultra-thin conformal silver films are the focus of development for applications such as anti-microbial surfaces, optical components and electronic devices. In this study, metallic silver films have been deposited using direct liq. injection thermal at. layer deposition (ALD) using (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) as the metal source and tert-Bu hydrazine (TBH) as a co-reactant. The process provides a 23 °C wide self-limiting ALD temp. window between 105 and 128 °C, which is significantly wider than is achievable using alc. as a co-reactant. A mass deposition rate of ∼20 ng/cm2/cycle (∼0.18 Å/cycle) is obsd. under self-limiting growth conditions. The resulting films are cryst. metallic silver with a near planar film-like morphol. which are elec. conductive. By extending the temp. range of the ALD window by the use of TBH as a co-reactant, it is envisaged that the process will be exploitable in a range of new low temp. applications.
- 23Hagen, D. J.; Connolly, J.; Povey, I. M.; Rushworth, S.; Pemble, M. E. Island Coalescence during Film Growth: An Underestimated Limitation of Cu ALD. Adv. Mater. Interfaces 2017, 4, 1700274, DOI: 10.1002/admi.201700274Google ScholarThere is no corresponding record for this reference.
- 24Li, Z.; Rahtu, A.; Gordon, R. G. Atomic Layer Deposition of Ultrathin Copper Metal Films from a Liquid Copper(I) Amidinate Precursor. J. Electrochem. Soc. 2006, 153, C787– C794, DOI: 10.1149/1.2338632Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XhtFeksb7I&md5=02e090476ba70213f186f685cf9589a9Atomic Layer Deposition of Ultrathin Copper Metal Films from a Liquid Copper(I) Amidinate PrecursorLi, Zhengwen; Rahtu, Antti; Gordon, Roy G.Journal of the Electrochemical Society (2006), 153 (11), C787-C794CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)We report a method for producing thin, completely continuous and highly conductive copper films conformally inside very narrow holes with aspect ratios over 35:1 by at. layer deposition (ALD). Pure copper thin films were grown from a novel copper(I) amidinate precursor, copper(I) N,N'-di-sec-butylacetamidinate, and mol. hydrogen gas as the reducing agent. This copper precursor is a liq. during vaporization because its m.p. (77°C) is lower than its vaporization temp. (90-120°C). Thus, the transport of the precursor vapor is very reproducible and controllable. Carbon and oxygen impurities were below 1 atom %. The growth per cycle varied from 1.5-2 A/cycle on SiO2 or Si3N4 surfaces but was only 0.1-0.5 A/cycle on metallic Ru, Cu, and Co surfaces. On oxide surfaces, copper atoms form isolated copper crystallites that merge into rough polycryst. films after more deposition cycles. On Ru and Co metal surfaces ALD Cu nucleates densely, forming smooth and strongly adherent films that are continuous even for films as thin as 4 at. layers. With 4 nm Cu deposited on 2 nm Ru substrates, the sheet resistance is below 50 Ω/.box., which is low enough for making seed layers for electroplating Cu interconnect wires.
- 25Martensson, P.; Carlsson, J. O. Atomic Layer Epitaxy of Copper Growth and Selectivity in the Cu(ll)-2,2,6,6-tetramethyl-3,5-heptanedionate/H2 Process. J. Electrochem. Soc. 1998, 145, 2926– 2931, DOI: 10.1149/1.1838738Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXltFGnsLw%253D&md5=1104c16a4d393d48fdf2569f1545c597Atomic layer epitaxy of copper growth and selectivity in the Cu(II)-2,2,6,6-tetramethyl-3,5-heptanedionate/H2 processMartensson, Per; Carlsson, Jan-OttoJournal of the Electrochemical Society (1998), 145 (8), 2926-2931CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)The deposition of Cu by at. layer epitaxy is reported. Using Cu(II)-2,2,6,6-tetramethyl-3,5-heptanedionate as the precursor, pure and specular Cu films were deposited at deposition temps. <200°. This is >150° lower than in previous reports for the same precursor where CVD was employed. The process was self-limited in the temp. range 190 to 260°. Area-selective deposition was achieved on Pt seeded substrates vs. unseeded glass slides or oxidized metal surfaces in the temp. range 175 to 300°. At higher temps., the selectivity was lost, and nucleation was independent of substrate material because of thermal decompn. of the precursor.
- 26Wack, S.; Lunca Popa, P.; Adjeroud, N.; Guillot, J.; Pistillo, B. R.; Leturcq, R. Large-Scale Deposition and Growth Mechanism of Silver Nanoparticles by Plasma-Enhanced Atomic Layer Deposition. J. Phys. Chem. C 2019, 123, 27196– 27206, DOI: 10.1021/acs.jpcc.9b06473Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvVylsLzI&md5=7de0be978c5ab3bcce10537d6ac4a448Large-Scale Deposition and Growth Mechanism of Silver Nanoparticles by Plasma-Enhanced Atomic Layer DepositionWack, Sabrina; Lunca Popa, Petru; Adjeroud, Noureddine; Guillot, Jerome; Pistillo, Bianca Rita; Leturcq, RenaudJournal of Physical Chemistry C (2019), 123 (44), 27196-27206CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The control of nanometer-scale metallic silver particles morphol. and their functional properties on a large scale represent a key factor for applications such as plasmonics, sensors, catalysts, or antimicrobial surfaces. The present work investigates in detail the growth of Ag nanoparticles deposited by plasma-enhanced at. layer deposition (PE-ALD), from triethylphosphine(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate)silver(I) [Ag(fod)(PEt3)-C16H25AgF7O2P] as the Ag precursor and H2 as the reducing agent. The uniformity of the deposition in terms of nanoparticle morphol. and chem. compn. over a large surface area (8 in.) is analyzed using an original method. For all morphol., crystallog., and chem. quantities, we report both the value at the center position and more originally, the gradient over a 10 cm distance on the substrate. The evolution of the gradient provides significant information on the growth mechanism. An effective growth rate of 0.020 ± 0.003 nm/cycle at 130 °C detd. by energy-dispersive X-ray spectroscopy is found uniformly over the whole 8-in. area of the sample. According to X-ray diffraction and X-ray photoemission spectroscopy performed on the whole silicon wafer, the deposited material is made of polycryst. pure metallic Ag, with a low amt. of impurities emanating from the precursor, showing the completeness of the redn. reaction. Under self-limiting conditions, the effects of the chamber temp. and cycle no. on the morphol. of Ag nanoparticles deposited on silicon are analyzed. The results suggests that the Ag thin films mainly evolve following a material transfer. Two potential mechanisms are in competition: the migration of the particles and their further coalescence through the Volmer-Weber growth mode or a "surface Ostwald ripening"-like process. Under certain conditions, this last mechanism could explain the nonuniformity of the deposition.
- 27Ni, C.; Shah, P.; Sarangan, A. M. Effects of different wetting layers on the growth of smooth ultra-thin silver thin films. In Proceedings of SPIE, Nanoengineering: Fabrication, Properties, Optics, and Devices XI; Campo, E. M.; Dobisz, E. A.; Eldada, L. A., Eds.; International Society for Optics and Photonics: San Diego, California, United States, August 2014 Vol. 9170.Google ScholarThere is no corresponding record for this reference.
- 28Lazzari, R.; Jupille, J. Silver Layers on Oxide Surfaces: Morphology and Optical Properties. Surf. Sci. 2001, 482-485, 823– 828, DOI: 10.1016/S0039-6028(01)00935-9Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXltVajt7o%253D&md5=0da472be7901200f304d555b5f139b35Silver layers on oxide surfaces. Morphology and optical propertiesLazzari, R.; Jupille, J.Surface Science (2001), 482-485 (Pt. 2), 823-828CODEN: SUSCAS; ISSN:0039-6028. (Elsevier Science B.V.)Trends in the wetting of oxide substrates by Ag are tested by surface differential reflectance via the detn. of the aspect ratio of the Ag clusters: (i) the wetting of α-Al2O3(0 0 0 1) substrates by Ag, which is quite poor, is strongly improved by Ti predeposition, provided that the Ti is metallic; (in particular, the exposure of the Ag/Ti/Al2O3 system to O leads to a dewetting of the Ag layer;) (ii) On a less insulating substrate than Al2O3 (8.9 eV band gap), the ZnO(0 0 0 1)-O surface (3.3 eV band gap), Ag forms clusters with much higher aspect ratio (diam./height) than on Al2O3. However, in all cases, Ag films growth in a Volmer-Weber mode.
- 29Chen, W.; Thoreson, M. D.; Ishii, S.; Kildishev, A. V.; Shalaev, V. M. Ultra-Thin Ultra-Smooth and Low-Loss Silver Films on a Germanium Wetting Layer. Opt. Express 2010, 18, 5124– 5134, DOI: 10.1364/OE.18.005124Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXivFOgs7o%253D&md5=69331605bc0182606cf2ea700df4a7a6Ultra-thin ultra-smooth and low-loss silver films on a germanium wetting layerChen, Weiqiang; Thoreson, Mark D.; Ishii, Satoshi; Kildishev, Alexander V.; Shalaev, Vladimir M.Optics Express (2010), 18 (5), 5124-5134CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)We demonstrate a method to fabricate ultra-thin, ultra-smooth and low-loss silver (Ag) films using a very thin germanium (Ge) layer as a wetting material and a rapid post-annealing treatment. The addn. of a Ge wetting layer greatly reduces the surface roughness of Ag films deposited on a glass substrate by electron-beam evapn. The percolation threshold of Ag films and the minimal thickness of a uniformly continuous Ag film were significantly reduced using a Ge wetting layer in the fabrication. A rapid post-annealing treatment is demonstrated to reduce the loss of the ultra-thin Ag film to the ideal values allowed by the quantum size effect in smaller grains. Using the same wetting method, we have also extended our studies to ultra-smooth silver-silica lamellar composite films with ultra-thin Ag sublayers.
- 30Stefaniuk, T.; Wróbel, P.; Trautman, P.; Szoplik, T. Ultrasmooth Metal Nanolayers for Plasmonic Applications: Surface Roughness and Specific Resistivity. Appl. Opt. 2014, 53, B237– B241, DOI: 10.1364/AO.53.00B237Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVSmur7J&md5=b5f5e48f0486f61812add21aea9d511fUltrasmooth metal nanolayers for plasmonic applications: surface roughness and specific resistivityStefaniuk, Tomasz; Wrobel, Piotr; Trautman, Pawel; Szoplik, TomaszApplied Optics (2014), 53 (10), B237-B241CODEN: APOPAI; ISSN:1559-128X. (Optical Society of America)The future of plasmonic devices depends on effective redn. of losses of surface plasmon-polariton waves propagating along metal-dielec. interfaces. Energy dissipation is caused by resistive heating at the skin-deep-thick outer layer of metal and scattering of surface waves on rough metal-dielec. interfaces. Fabrication of noble metal nanolayers with a smooth surface still remains a challenge. In this paper, Ag layers of 10, 30, and 50 nm thickness deposited directly on fused-silica substrates and with a 1 nm wetting layer of Ge, Ti, and Ni are examd. using an at.-force microscope and four-probe resistivity measurements. In the case of all three wetting layers, the specific resistivity of silver film decreases as the thickness increases. The smallest, equal 0.4 nm root mean squared roughness of Ag surface of 10 nm thickness is achieved for Ge interlayer; however, due to Ge segregation the specific resistivity of silver film in Ag/Ge/SiO2 structures is about twice higher than that in Ag/Ti/SiO2 and Ag/Ni/SiO2 sandwiches.
- 31Formica, N.; Ghosh, D. S.; Carrilero, A.; Chen, T. L.; Simpson, R. E.; Pruneri, V. Ultrastable and Atomically Smooth Ultrathin Silver Films Grown on a Copper Seed Layer. ACS Appl. Mater. Interfaces 2013, 5, 3048– 3053, DOI: 10.1021/am303147wGoogle Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktlyksrg%253D&md5=4edcd67260971eca7375eae4a5bd6919Ultrastable and Atomically Smooth Ultrathin Silver Films Grown on a Copper Seed LayerFormica, Nadia; Ghosh, Dhriti S.; Carrilero, Albert; Chen, Tong Lai; Simpson, Robert E.; Pruneri, ValerioACS Applied Materials & Interfaces (2013), 5 (8), 3048-3053CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)An effective method to deposit atomically smooth ultrathin silver (Ag) films by employing a 1 nm copper (Cu) seed layer is reported. The inclusion of the Cu seed layer leads to the deposition of films with extremely low surface roughness (<0.5 nm), while it also reduces the min. thickness required to obtain a continuous Ag film (percolation thickness) to 3 nm compared with 6 nm without the seed layer. Moreover, the Cu seed layer alters the growth mechanism of the Ag film by providing energetically favorable nucleation sites for the incoming Ag atoms leading to an improved surface morphol. and concomitant lower elec. sheet resistance. Optical measurements together with X-ray diffraction and elec. resistivity measurements confirmed that the Ag film undergoes a layer-by-layer growth mode resulting in a smaller grain size. The Cu seeded Ag growth method provides a feasible way to deposit ultrathin Ag films for nanoscale electronic, plasmonic, and photonic applications. In addn., as a result of the improved uniformity, the oxidn. of the Ag layer is strongly reduced to negligible values.
- 32Alvarez, R.; González, J. C.; Espinós, J. P.; González-Elipe, A. R.; Cueva, A.; Villuendas, F. Growth of Silver on ZnO And SnO2 Thin Films Intended for Low Emissivity Applications. Appl. Surf. Sci. 2013, 268, 507– 515, DOI: 10.1016/j.apsusc.2012.12.156Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtF2gt70%253D&md5=065e7b3be2aec732e5243ddf140a76e0Growth of silver on ZnO and SnO2 thin films intended for low emissivity applicationsAlvarez, Rafael; Gonzalez, Juan C.; Espinos, Juan P.; Gonzalez-Elipe, Agustin R.; Cueva, Ana; Villuendas, FranciscoApplied Surface Science (2013), 268 (), 507-515CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)The authors have investigated the relationships existing between the optical properties and the growth mechanism, microstructure, and surface roughness of SnO2 and ZnO oxide films prepd. by magnetron sputtering under conditions resembling those utilized in industry. Thin films of these oxides with different thicknesses were characterized by at. force microscopy, glancing incidence X-ray diffraction (GIXRD), X-ray reflectometry, and spectroscopic ellipsometry. The roughness evolution of the film properties (d., surface roughness, and refraction index) as a function of their thickness has been evaluated within the concepts of the Dynamic Scaling Theory of thin film growth. Zinc oxide films were rougher than tin oxide films of similar thickness, indicating a different growing mechanism for the two materials. Silver was evapd. onto the surface of the two oxide thin films and its earlier stages of nucleation studied by background anal. of the X-ray photoemission spectra. A different nucleation mechanism was found depending on the nature of the oxide acting as substrate. The superior performance of the zinc oxide based low emissive coatings is related with a better wetting of silver on the surface of this oxide despite the comparatively lower roughness of the tin oxide layers.
- 33Zhang, C.; Kinsey, N.; Chen, L.; Ji, C.; Xu, M.; Ferrera, M.; Pan, X.; Shalaev, V. M.; Boltasseva, A.; Guo, L. J. High-Performance Doped Silver Films: Overcoming Fundamental Material Limits for Nanophotonic Applications. Adv. Mater. 2017, 29, 1605177, DOI: 10.1002/adma.201605177Google ScholarThere is no corresponding record for this reference.
- 34Masango, S. S.; Peng, L.; Marks, L. D.; Van Duyne, R. P.; Stair, P. C. Nucleation and Growth of Silver Nanoparticles by AB and ABC-Type Atomic Layer Deposition. J. Phys. Chem. C 2014, 118, 17655– 17661, DOI: 10.1021/jp504067cGoogle Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtFChur%252FI&md5=31d8bc5461e48ec61f5d96f0b99ba8adNucleation and Growth of Silver Nanoparticles by AB and ABC-Type Atomic Layer DepositionMasango, Sicelo S.; Peng, Lingxuan; Marks, Laurence D.; Van Duyne, Richard P.; Stair, Peter C.Journal of Physical Chemistry C (2014), 118 (31), 17655-17661CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Synthesis strategies to produce Ag nanoparticles by AB-type and ABC-type at. layer deposition (ALD) using trimethylphosphine(hexafluoroacetylacetonato) silver(I) ((hfac)Ag(PMe3)) and formalin (AB-type) and (hfac)Ag(PMe3), trimethylaluminum, and H2O (ABC-type) are reported. In situ quartz crystal microbalance measurements reveal an Ag growth rate of 1-2 ng/cm2/cycle by ABC-type ALD at 110°C and 2-10 ng/cm2/cycle for AB-type ALD at 170-200°C. AB-type Ag ALD has a nucleation period before continuous linear growth that is shorter at 200°C. Transmission electron microscopy reveals that AB-type Ag ALD particles have an av. size of ∼1.8 nm after 10 cycles. ABC-type Ag ALD particles have an av. size of ∼2.2 nm after 20 cycles. With increasing ALD cycles, ABC-type Ag ALD increases the metal loading while maintaining the particle size but AB-type Ag ALD results in the formation of bigger particles in addn. to small particles. The ability to synthesize supported metal nanoparticles with well-defined particle sizes and narrow size distributions makes ALD an attractive synthesis method compared with conventional wet chem. techniques.
- 35Dhakal, D.; Assim, K.; Lang, H.; Bruener, P.; Grehl, T.; Georgi, C.; Waechtler, T.; Ecke, R.; Schulz, S. E.; Gessner, T. Atomic Layer Deposition of Ultrathin Cu2O and Subsequent Reduction to Cu Studied by In Situ X-Ray Photoelectron Spectroscopy. J. Vac. Sci. Technol., A 2016, 34, 01A111 DOI: 10.1116/1.4933088Google ScholarThere is no corresponding record for this reference.
- 36Goldstein, J. I.; Newbury, D. E.; Michael, J. R.; Ritchie, N. W.; Scott, J. H. J.; Joy, D. C. Scanning Electron Microscopy and X-ray Microanalysis; 3rd ed.; Springer: New-York, 2003.Google ScholarThere is no corresponding record for this reference.
- 37Kyser, D. F.; Murata, K. Quantitative Electron Microprobe Analysis of Thin Films on Substrates. IBM J. Res. Dev. 1974, 18, 352– 363, DOI: 10.1147/rd.184.0352Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2cXltFCitbY%253D&md5=8edc8a6b9e2e4673674401b416f409faQuantitative electron microprobe analysis of thin films on substratesKyser, D. F.; Murata, K.IBM Journal of Research and Development (1974), 18 (4), 352-63CODEN: IBMJAE; ISSN:0018-8646.A Monte Carlo simulation procedure was developed for kV electron beam scattering and energy loss in target consisting of thin films on thick substrates; the calcns. have direct application to the nondestructive quant. anal. of ultra thin films with an electron microprobe. Angular elastic scattering is calcd. in the electron trajectory simulation with the screened Rutherford expression for cross section, and energy loss between elastic scattering events is calcd. by using the approxn. of Bethe. The contribution to x-ray fluorescence from the film owing to backscattered electrons from the substrate is taken into account. For elemental films the simulation predicts intensity ratios for characteristic x-rays from the films, referred to stds. of thick elemental samples. No film stds. are required, and the mass thickness of any film element on any substrate can be detd. from theor. calibration curves. The model was verified by measurements on films of Si, Cu, and Au on Al2O3, and Mn-Bi and Co-Pt films with total mass thicknesses ≤100 μg/cm2 were successfully analyzed.
- 38Murata, K.; Kotera, M.; Nagami, K. Quantitative Electron Microprobe Analysis of Thin Films on Substrates with a New Monte Carlo Simulation. J. Appl. Phys. 1983, 54, 1110– 1114, DOI: 10.1063/1.332127Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3sXhtFylsLo%253D&md5=81e9b5d5522cff045de8d0906b5d6c79Quantitative electron microprobe analysis of thin films on substrates with a new Monte Carlo simulationMurata, Kenji; Kotera, Masatoshi; Nagami, KoichiJournal of Applied Physics (1983), 54 (2), 1110-14CODEN: JAPIAU; ISSN:0021-8979.A new Monte Carlo simulation was applied to the electron microprobe anal. of thin films at energies 1-10 keV. The simulation model utilizes the Mott cross section for elastic scattering and the modified Bethe equation of Rao Sahib-Wittry for energy loss, instead of the screened Rutherford cross section and the std. Bethe equation, resp. The new model was examd. in comparison with exptl. results for the most probable angle of transmitted electrons through a thin film, and also the depth distribution of x-ray prodn. The simulation was applied to thickness anal. of both Al and Au films on a sapphire substrate. The new results show good agreement with exptl. data. The new Monte Carlo simulation is useful for electron microprobe anal. for elements, esp. for heavy materials at relatively low energies.
- 39Murata, K.; Sugiyama, K. Quantitative Electron Microprobe Analysis of Ultrathin Gold Films on Substrates. J. Appl. Phys. 1989, 66, 4456– 4461, DOI: 10.1063/1.343942Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3cXhsVyitg%253D%253D&md5=c4cf7e66d7a9a371e0c6d81086df82beQuantitative electron microprobe analysis of ultrathin gold films on substratesMurata, Kenji; Sugiyama, KatsuyaJournal of Applied Physics (1989), 66 (9), 4456-61CODEN: JAPIAU; ISSN:0021-8979.The thickness of gold thin films of 0.1-100 nm on Si substrates has been measured with an electron probe microanalyzer. The measured thickness results agree very well with exptl. ones, which are obtained with a quartz balance app. The thickness detection limit of the present method can reach submonolayer films.
- 40Campos, C. S.; Vasconcellos, M. A. Z.; Llovet, X.; Salvat, F. Thickness Determination of Ultra-Thin Films on Si Substrates by EPMA. Microchim. Acta 2004, 145, 13– 17, DOI: 10.1007/s00604-003-0120-3Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjsVWjsb8%253D&md5=aeb4c4fc6473bec9f5c41f4a9302094dThickness determination of ultrathin films on silicon substrates by EPMACampos, Christiani S.; Vasconcellos, Marcos A. Z.; Llovet, Xavier; Salvat, FrancescMicrochimica Acta (2004), 145 (1-4), 13-17CODEN: MIACAQ; ISSN:0026-3672. (Springer-Verlag Wien)Results from thickness detn. of single-element ultrathin (<10 nm) films by electron probe microanal. (EPMA) are presented. The studied samples were Ge, Sn, Ag, and Au thin films deposited by resistive evapn. on Si substrates. The thickness of the films was controlled during evapn. by means of a quartz crystal, previously calibrated using samples with overlayers of different thicknesses (>20 nm) measured by Rutherford backscatter spectrometry and optical interferometry. EPMA measurements were performed on an electron microprobe CAMECA SX-50, with incident electron energies ranging from 4 keV to 20 keV. Film thicknesses were derived from the measured k-ratios using the anal. programs X-Film and Layerf and the Monte Carlo simulation code Penelope. The ionization cross sections used in the simulations were calcd. with the distorted-wave Born approxn. Film thicknesses obtained from the EPMA measurements using the various computational methods are compared with those measured with the quartz crystal. The max. relative difference between results from the different techniques does not exceed 5%.
- 41Drouin, D.; Couture, A. R.; Joly, D.; Tastet, X.; Aimez, V.; Gauvin, R. CASINO V2.42–A Fast and Easy-to-use Modeling Tool for Scanning Electron Microscopy and Microanalysis Users. Scanning 2007, 29, 92– 101, DOI: 10.1002/sca.20000Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnvVensL4%253D&md5=40f92d9c001f910844da3e298d18fb42CASINO V2.42-a fast and easy-to-use modeling tool for scanning electron microscopy and microanalysis usersDrouin, Dominique; Couture, Alexandre Real; Joly, Dany; Tastet, Xavier; Aimez, Vincent; Gauvin, RaynaldScanning (2007), 29 (3), 92-101CODEN: SCNNDF; ISSN:0161-0457. (John Wiley & Sons Ltd.)Monte Carlo simulations have been widely used by microscopists for the last few decades. In the beginning it was a tedious and slow process, requiring a high level of computer skills from users and long computational times. Recent progress in the microelectronics industry now provides researchers with affordable desktop computers with clock rates greater than 3 GHz. With this type of computing power routinely available, Monte Carlo simulation is no longer an exclusive or long (overnight) process. The aim of this paper is to present a new user-friendly simulation program based on the earlier CASINO Monte Carlo program. The intent of this software is to assist scanning electron microscope users in interpretation of imaging and microanal. and also with more advanced procedures including electron-beam lithog. This version uses a new architecture that provides results twice as quickly. This program is freely available to the scientific community and can be downloaded from the website: www.gel.usherb.ca/casino.
- 42Drouin, D.; Hovington, P.; Gauvin, R. CASINO: A New Monte Carlo Code in C Language for Electron Beam Interactions–Part II: Tabulated Values of the Mott Cross Section. Scanning 1997, 19, 20– 28, DOI: 10.1002/sca.4950190103Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmvFynsro%253D&md5=24d300f3ab7a4f9f4a0df5ac87ecba69CASINO: a new Monte Carlo code in C language for electron beam interactions - part II: Tabulated values of the Mott cross sectionDrouin, Dominique; Hovington, Pierre; Gauvin, RaynaldScanning (1997), 19 (1), 20-28CODEN: SCNNDF; ISSN:0161-0457. (FAMS, Inc.)This paper presents routines to compute the Mott cross section used in the CASINO program (Monte CArlo SImulation of electroN trajectory in sOlid). The routines used tabulated values of the Mott cross section computed in the work of Czyzewski et al. (1990). The cross section is available over the range 0.02 to 30 keV and for the first 94 elements of the Periodic Table. The routines are written in C language and use a binary file to interpolate the cross section. The first routine computes the total Mott cross sections; the second calcs. the polar angle of collision. Backscattered coeffs. computed using different cross section are compared for C, Al, Ag, and Au. The Rutherford (1911) cross section and the available empirical equations (Browning et al. 1994, Gauvin and Drouin 1993) are compared to tabulated values of Mott. Also, the energy distribution of backscattered electrons is shown for Al and Au at 10 keV. Finally, the relative computation times for the different Mott cross sections are compared. It was found that tabulated Mott cross sections are more accurate and faster than any empirical Mott cross sections. The tabulated Mott cross sections are even faster than simple Rutherford cross sections.
- 43Hovington, P.; Drouin, D.; Gauvin, R. CASINO: A New Monte Carlo Code in C Language for Electron Beam Interaction–Part I: Description of the Program. Scanning 1997, 19, 1– 14, DOI: 10.1002/sca.4950190101Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmvFynsr0%253D&md5=a445397baf9fd4af8694601b5cb66178CASINO: a new Monte Carlo code in C language for electron beam interaction - part I: Description of the programHovington, Pierre; Drouin, Dominique; Gauvin, RaynaldScanning (1997), 19 (1), 1-14CODEN: SCNNDF; ISSN:0161-0457. (FAMS, Inc.)This paper is a guide to the ANSI std. C code of CASINO program which is a single scattering Monte CArlo SImulation of electroN trajectory in sOlid specially designed for low-beam interaction in a bulk and thin foil. CASINO can be used either on a DOS-based PC or on a UNIX-based workstation. This program uses tabulated Mott elastic cross sections and exptl. detd. stopping powers. Function pointers are used for the most essential routine so that different phys. models can easily be implemented. CASINO can be used to generate all of the recorded signals (x-rays, secondary, and backscattered) in a scanning electron microscope either as a point anal., as a linescan, or as an image format, for all the accelerated voltages (0.1-30 kV). As an example of application, it was found that a 20 nm Guinier-Preston Mg2Si in a light aluminum matrix can, theor., be imaged with a microchannel backscattered detector at 5 keV with a beam spot size of 5 nm.
- 44Arts, K.; Vandalon, V.; Puurunen, R. L.; Utriainen, M.; Gao, F.; Kessels, W. M. M.; Knoops, H. C. M. Sticking Probabilities of H2O and Al(CH3)3 During Atomic Layer Deposition of Al2O3 Extracted from their Impact on Film Conformality. J. Vac. Sci. Technol., A 2019, 37, 030908 DOI: 10.1116/1.5093620Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXosVOns74%253D&md5=9b0d5be3ba07ae8b06cdec6c59b2de73Sticking probabilities of H2O and Al(CH3)3 during atomic layer deposition of Al2O3 extracted from their impact on film conformalityArts, Karsten; Vandalon, Vincent; Puurunen, Riikka L.; Utriainen, Mikko; Gao, Feng; Kessels, Wilhelmus M. M.; Knoops, Harm C. M.Journal of Vacuum Science & Technology, A: Vacuum, Surfaces, and Films (2019), 37 (3), 030908/1-030908/5CODEN: JVTAD6; ISSN:0734-2101. (American Institute of Physics)The conformality of a film grown by at. layer deposition (ALD) is strongly affected by the reactivities of the precursor and coreactant, which can be expressed in terms of their sticking probabilities toward the surface. We show that the leading front of the thickness profile in high-aspect-ratio structures gives direct information on the sticking probabilities of the reactants under most conditions. The slope of the front has been used to det. the sticking probabilities of Al(CH3)3 and H2O during ALD of Al2O3. The detd. values are (0.5-2) × 10-3 for Al(CH3)3 and (0.8-2) × 10-4 for H2O at a set-point temp. of 275°C, corresponding to an estd. substrate temp. of 220°C. Addnl., the thickness profiles reveal soft-satn. behavior during the H2O step, most dominantly at reduced temps., which can limit the conformality of Al2O3 grown by ALD. This work thus provides insights regarding quant. information on sticking probabilities and conformality during ALD, which is valuable for gaining a deeper understanding of ALD kinetics. (c) 2019 American Institute of Physics.
- 45Gao, F.; Arpiainen, S.; Puurunen, R. Microscopic Silicon-Based Lateral High-Aspect-Ratio Structures for Thin Film Conformality Analysolis. J. Vac. Sci. Technol., A 2015, 33, 010601 DOI: 10.1116/1.4903941Google Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitFOjsL%252FL&md5=0a4a6c187a220ba60158e005986d29abMicroscopic silicon-based lateral high-aspect-ratio structures for thin film conformality analysisGao, Feng; Arpiainen, Sanna; Puurunen, Riikka L.Journal of Vacuum Science & Technology, A: Vacuum, Surfaces, and Films (2015), 33 (1), 010601/1-010601/5CODEN: JVTAD6; ISSN:0734-2101. (American Institute of Physics)Film conformality is one of the major drivers for the interest in at. layer deposition (ALD) processes. This work presents new silicon-based microscopic lateral high-aspect-ratio (LHAR) test structures for the anal. of the conformality of thin films deposited by ALD and by other chem. vapor deposition means. The microscopic LHAR structures consist of a lateral cavity inside silicon with a roof supported by pillars. The cavity length (e.g., 20-5000 μm) and cavity height (e.g., 200-1000 nm) can be varied, giving aspect ratios of, e.g., 20:1 to 25 000:1. Film conformality can be analyzed with the microscopic LHAR by several means, as demonstrated for the ALD Al2O3 and TiO2 processes from Me3Al/H2O and TiCl4/H2O. The microscopic LHAR test structures introduced in this work expose a new parameter space for thin film conformality investigations expected to prove useful in the development, tuning and modeling of ALD and other chem. vapor deposition processes. (c) 2015 American Institute of Physics.
- 46Prokes, S. M.; Glembocki, O. J.; Cleveland, E.; Caldwell, J. D.; Foos, E.; Niinistö, J.; Ritala, M. Spoof-Like Plasmonic Behavior of Plasma Enhanced Atomic Layer Deposition Grown Ag Thin Films. Appl. Phys. Lett. 2012, 100, 053106 DOI: 10.1063/1.3679106Google Scholar46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsVaqu78%253D&md5=b04b5846473ce964e0a89c012cda82caSpoof-like plasmonic behavior of plasma enhanced atomic layer deposition grown Ag thin filmsProkes, S. M.; Glembocki, O. J.; Cleveland, Erin; Caldwell, Josh D.; Foos, Edward; Niinistoe, Jaakko; Ritala, MikkoApplied Physics Letters (2012), 100 (5), 053106/1-053106/3CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)The plasmonic behavior of Ag thin films produced by plasma enhanced at. layer deposition (PEALD) was studied. As-deposited flat PEALD Ag films exhibit unexpected plasmonic properties, and the plasmonic enhancement can differ markedly, depending on the microstructure of the Ag film. Electromagnetic field simulations indicate that this plasmonic behavior is due to air gaps that are an inherent property of the mosaic-like microstructure of the PEALD-grown Ag film, suggesting that this is a metamaterial with behavior very similar to what would be expected in spoof plasmonics where gaps are fabricated in films to create plasmonic-like resonances. (c) 2012 American Institute of Physics.
- 47Van den Bruele, F. J.; Smets, M.; Illiberi, A.; Creyghton, Y.; Buskens, P.; Roozeboom, F.; Poodt, P. Atmospheric Pressure Plasma Enhanced Spatial ALD of Silver. J. Vac. Sci. Technol., A 2015, 33, 01A131 DOI: 10.1116/1.4902561Google ScholarThere is no corresponding record for this reference.
- 48Emslie, D. J. H.; Chadha, P.; Price, J. S. Metal ALD and Pulsed CVD: Fundamental Reactions and Links with Solution Chemistry. Coord. Chem. Rev. 2013, 257, 3282– 3296, DOI: 10.1016/j.ccr.2013.07.010Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs1KitrjI&md5=a3900319eabfd17cf77cc9666a09c75fMetal ALD and pulsed CVD: Fundamental reactions and links with solution chemistryEmslie, David J. H.; Chadha, Preeti; Price, Jeffrey S.Coordination Chemistry Reviews (2013), 257 (23-24), 3282-3296CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)A review. At. layer deposition (ALD) is a thin film deposition technique which operates via repeated alternating and self-terminating surface-based reactions between a precursor and a co-reactant, sepd. in time by purge steps. This technique is particularly well-suited to the deposition of highly uniform and conformal thin films, even on surfaces with nano-scale high aspect ratio features. Furthermore, use of a metal precursor and a co-reactant in ALD and the related technique of pulsed-CVD (pulsed-chem. vapor deposition), provides the potential for deposition of materials that may be inaccessible using CVD methods that rely upon the thermal decompn. of a single metal precursor. This review surveys the different classes of co-reactant used for thermal metal ALD/pulsed-CVD with a focus on the reaction chemistries known or proposed to be involved. Parallels are drawn between surface-based metal ALD/pulsed-CVD reactivity and soln.-based reactivity including electroless deposition, soln.-based nanoparticle prepn., and the prepn. of zero-valent complexes bearing labile ligands. Also described are applications of soln. screening and soln. mechanistic studies to the identification of promising new ALD/pulsed-CVD reactivities, and the generation of initial mechanistic hypotheses as to the fundamental reaction steps involved in metal ALD/pulsed-CVD. A primary goal of this review is to provide a unique reactivity-based perspective of metal ALD/pulsed-CVD. In addn., endeavored to illustrate commonalities between soln.-based and surface-based reactions relevant to metal deposition, and to highlight beneficial applications of the former to the development of the latter.
- 49Vidjayacoumar, B.; Emslie, D. J. H.; Clendenning, S. B.; Blackwell, J. M.; Britten, J. F.; Rheingold, A. Investigation of AlMe3, BEt3, and ZnEt2 as Co-Reagents for Low-Temperature Copper Metal ALD/Pulsed-CVD. Chem. Mater. 2010, 22, 4844– 4853, DOI: 10.1021/cm101442eGoogle Scholar49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXpvFSmtbs%253D&md5=02106bc3663edb01731b20e93eec7fd1Investigation of AlMe3, BEt3, and ZnEt2 as Co-Reagents for Low-Temperature Copper Metal ALD/Pulsed-CVDVidjayacoumar, Balamurugan; Emslie, David J. H.; Clendenning, Scott B.; Blackwell, James M.; Britten, James F.; Rheingold, ArnoldChemistry of Materials (2010), 22 (17), 4844-4853CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)The reactions of AlMe3, BEt3, and ZnEt2 with toluene solns. of the copper(II) complexes [CuL2] {L = acetylacetonate (acac; 1), hexafluoroacetylacetonate (hfac; 2), N-isopropyl-β-ketiminate (acnac; 3), N,N-dimethyl-β-diketiminate (nacnac; 4), 2-pyrrolylaldehyde (PyrAld; 5), N-isopropyl-2-pyrrolylaldiminate (PyrImiPr; 6a), N-ethyl-2-pyrrolylaldiminate (PyrImEt; 6b), and N-isopropyl-2-salicylaldiminate (IPSA; 7)} were investigated, and most combinations were found to deposit metal films or metal powder at 50 °C or less. SEM and XPS of metal films deposited on ruthenium showed a range of morphologies and compns., including pure copper (excluding oxygen content after atm. exposure). These nonaq. soln. screening studies provided a rapid and convenient means to identify the most promising [CuIIL2] precursor/ERn co-reagent combinations for copper metal ALD/pulsed-CVD studies, and subsequent ALD/pulsed-CVD studies were performed using 6b in combination with AlMe3, BEt3 and ZnEt2. As in soln., the reactivity of these reagents (pulsed-CVD) followed the order ZnEt2 ≈ AlMe3 » BEt3. Furthermore, at 120-150 °C, ZnEt2 was used successfully to deposit smooth, conductive films composed of copper with 8-15% Zn. On the basis of CVD studies with ZnEt2, zinc content appears to derive from a parasitic CVD process, which becomes more favorable above 120 °C, detracting from the goal of self-limiting deposition.
- 50Raut, N. C.; Al-Shamery, K. Inkjet Printing Metals on Flexible Materials for Plastic and Paper Electronics. J. Mater. Chem. C 2018, 6, 1618– 1641, DOI: 10.1039/C7TC04804AGoogle Scholar50https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXksFOqtw%253D%253D&md5=46a12e26247c875fa52714f2a44edc3eInkjet printing metals on flexible materials for plastic and paper electronicsRaut, N. C.; Al-Shamery, K.Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (7), 1618-1641CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)Inorg. printed electronics is now recognized as an area of tremendous com., potential and tech. progress. Many research groups are actively involved worldwide in developing metal nanoparticle inks and precursors for printing inorg./org. materials using different printing techniques. This review article focuses on inkjet printed metal structures and their applications. It comprises ink formulation, optimal droplet formation as well as adhesion of the printed patterns at the underlying substrate and post-treatment like sintering to be considered in the initial ink design. Besides some examples demonstrating aspects on ink formulation via patterning solid surfaces such as glass and silicon oxide, special emphasis will be placed on compatibility for usage in plastic and paper electronics. Printing of nanoparticles of copper, silver, gold etc. will be discussed and will be compared to printing of a variety of metal-org. precursor inks. Finally, a brief account on exemplary applications using the printed inorg. nanoparticles/materials is provided.
- 51Mo, L.; Guo, Z.; Yang, L.; Zhang, Q.; Fang, Y.; Xin, Z.; Chen, Z.; Hu, K.; Han, L.; Li, L. Silver Nanoparticles Based Ink with Moderate Sintering in Flexible and Printed Electronics. Int. J. Mol. Sci. 2019, 20, 2124, DOI: 10.3390/ijms20092124Google Scholar51https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtFKis7Y%253D&md5=032edfe9c3486926af3fa4d632f8b4faSilver nanoparticles based ink with moderate sintering in flexible and printed electronicsMo, Lixin; Guo, Zhenxin; Yang, Li; Zhang, Qingqing; Fang, Yi; Xin, Zhiqing; Chen, Zheng; Hu, Kun; Han, Lu; Li, LuhaiInternational Journal of Molecular Sciences (2019), 20 (9), 2124CODEN: IJMCFK; ISSN:1422-0067. (MDPI AG)A review. Printed electronics on flexible substrates has attracted tremendous research interest research thanks its low cost, large area prodn. capability and environmentally friendly advantages. Optimal characteristics of silver nanoparticles (Ag NPs) based inks are crucial for ink rheol., printing, post-print treatment, and performance of the printed electronics devices. In this review, the methods and mechanisms for obtaining Ag NPs based inks that are highly conductive under moderate sintering conditions are summarized. These characteristics are particularly important when printed on temp. sensitive substrates that cannot withstand sintering of high temp. Strategies to tailor the protective agents capping on the surface of Ag NPs, in order to optimize the sizes and shapes of Ag NPs as well as to modify the substrate surface, are presented. Different (emerging) sintering technologies are also discussed, including photonic sintering, elec. sintering, plasma sintering, microwave sintering, etc. Finally, applications of the Ag NPs based ink in transparent conductive film (TCF), thin film transistor (TFT), biosensor, radio frequency identification (RFID) antenna, stretchable electronics and their perspectives on flexible and printed electronics are presented.
- 52Lienhart, R. FR Patent. 015113, 2015.Google ScholarThere is no corresponding record for this reference.
- 53Gaarenstroom, S. W.; Winograd, N. Initial and Final State Effects in the ESCA Spectra of Cadmium and Silver Oxides. J. Chem. Phys. 1977, 67, 3500– 3506, DOI: 10.1063/1.435347Google Scholar53https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE1cXotFGhtw%253D%253D&md5=457dc2e5101c0285a000550e2ca71b69Initial and final state effects in the ESCA spectra of cadmium and silver oxidesGaarenstroom, S. W.; Winograd, N.Journal of Chemical Physics (1977), 67 (8), 3500-6CODEN: JCPSA6; ISSN:0021-9606.The factors which influence chem. shifts are examd. in order to elucidate the cause of the anomalous chem. shifts for Cd and Ag oxides. The effects of extra-at. relaxation are accounted for using a procedure employing exptl. Auger and binding energies. At. partial ionic charges for some simple Cd, Ag, and Zn compds. are calcd. from exptl. binding energies using a model which includes the effects of lattice potentials and extra-at. relaxation. Inclusion of extra-at. relaxation effects did not have a drastic effect on the relative ionicities computed for these selected compds. However, for CdO, a large extra-at. relaxation energy contribution reduces the binding energy by 0.5 eV more than is predicted from nearest electroneg. arguments.
- 54Moulder, J. F.; Stickle, W. F.; Sobol, P. E.; Bomben, K. D. Physical Electronics Division. Handbook of X-ray Photoelectron Spectroscopy; Chastain, J., Ed.; Perkin-Elmer Corporation: Eden Prairie, Minnesota, United States, 1995.Google ScholarThere is no corresponding record for this reference.
- 55Birkholz, M.; Fewster, P. F.; Genzel, C. Thin Film Analysis by X-ray Scattering; Wiley-VCH : Weinheim, 2006.Google ScholarThere is no corresponding record for this reference.
- 56de Keijser, T. H.; Langford, J. I.; Mittemeijer, E. J.; Vogels, A. B. P. Use of the Voigt Function in a Single-Line Method for the Analysis of X-ray Diffraction Line Broadening. J. Appl. Crystallogr. 1982, 15, 308– 314, DOI: 10.1107/S0021889882012035Google Scholar56https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL38XitVyrsrs%253D&md5=2600c53296f378634db7abe47d338338Use of the Voigt function in a single-line method for the analysis of x-ray diffraction line broadeningDe Keijser, T. H.; Langford, J. I.; Mittemeijer, E. J.; Vogels, A. B. P.Journal of Applied Crystallography (1982), 15 (3), 308-14CODEN: JACGAR; ISSN:0021-8898.The use of the Voigt function for the anal. of the integral breadths of broadened x-ray diffraction line profiles forms the basis of a rapid and powerful single-line method of crystallite-size and strain detn. which is easy to apply. To avoid graphical methods or interpolation from tables, empirical formulae of high accuracy are used and an estn. of errors is presented, including the influence of line-profile asymmetry. The method applied to four practical cases of size-strain broadening: (1) cold-worked Ni, (2) a nitrided steel, (3) an electrodeposited Ni layer, and (4) a liq.-quenched A-Si alloy.
- 57Johnson, P. B.; Christy, R. W. Optical Constants of the Noble Metals. Phys. Rev. B 1972, 6, 4370– 4379, DOI: 10.1103/PhysRevB.6.4370Google Scholar57https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3sXjsFKksA%253D%253D&md5=d960c3d9476f6cabad9562e5ea3a9d6cOptical constants of the noble metalsJohnson, P. B.; Christy, R. W.Physical Review B: Solid State (1972), 6 (12), 4370-9CODEN: PLRBAQ; ISSN:0556-2805.The optical consts. n and k were obtained for Cu, Ag, and Au from reflection and transmission measurements on vacuum-evapd. thin films at room temp., in the spectral range 0.5-6.5 eV. The film-thickness range was 185-500 Å. Three optical measurements were inverted to obtain the film thickness d as well as n and k. The estd. error in d was ±2 Å, and that in n, k was <0.02 over most of the spectral range. The results in the film-thickness range 250-500 Å were independent of thickness, and were unchanged after vacuum annealing or aging in air. The free-electron optical effective masses and relaxation times derived from the results in the near ir agreed satisfactorily with previous values. The interband contribution to the imaginary part of the dielec. const. was obtained by subtracting the free-electron contribution. Some recent theor. calcns. were compared with the results for Cu and Au. In addn., some other recent expts. are crit. compared with the present results.
- 58Amendola, V.; Bakr, O. M.; Stellacci, F. A Study of the Surface Plasmon Resonance of Silver Nanoparticles by the Discrete Dipole Approximation Method: Effect of Shape, Size, Structure, and Assembly. Plasmonics 2010, 5, 85– 97, DOI: 10.1007/s11468-009-9120-4Google Scholar58https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjtlGnt7s%253D&md5=65ece8c3f63e53ac871ed0fff4ab399cA Study of the Surface Plasmon Resonance of Silver Nanoparticles by the Discrete Dipole Approximation Method: Effect of Shape, Size, Structure, and AssemblyAmendola, Vincenzo; Bakr, Osman M.; Stellacci, FrancescoPlasmonics (2010), 5 (1), 85-97CODEN: PLASCS; ISSN:1557-1955. (Springer)The surface plasmon resonance (SPR) of silver nanoparticles (AgNPs) was studied with the discrete dipole approxn. considering different shapes, sizes, dielec. environments, and supra-particles assemblies. In particular, we focused our simulations on AgNPs with sizes below 10 nm, where the correction of silver dielec. const. for intrinsic size effects is necessary. We found that AgNPs shape and assembly can induce distinctive features in the extinction spectra and that SPR is more intense when AgNPs have discoid or flat shapes and are embedded in a dielec. shell with high refractive index. However, the SPR loses much of its distinctive features when size effects and stabilizing mols. induce significant broadening of the extinction bands that is often obsd. in the case of thiolated AgNPs smaller than about 5 nm. These results are useful indications for in situ characterization and monitoring of AgNPs synthesis and for the engineering of AgNPs with new plasmonic properties.
- 59Drachev, V. P.; Perminov, S. V.; Rautian, S. G.; Safonov, V. P. Nonlinear Optical Effects and Selective Photomodification of Colloidal Silver Aggregates. Top. Appl. Phys. 2002, 82, 115, DOI: 10.1007/3-540-44948-5_6Google ScholarThere is no corresponding record for this reference.
- 60Kato, K.; Omoto, H.; Tomioka, T.; Takamatsu, A. Visible and Near Infrared Light Absorbance of Ag Thin Films Deposited On ZnO Under Layers by Magnetron Sputtering. Sol. Energy Mater. Sol. Cells 2011, 95, 2352– 2356, DOI: 10.1016/j.solmat.2011.04.005Google Scholar60https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXntlWrtLw%253D&md5=885f0e812fce1d2a3b69c0699abf23baVisible and near infrared light absorbance of Ag thin films deposited on ZnO under layers by magnetron sputteringKato, Kazuhiro; Omoto, Hideo; Tomioka, Takao; Takamatsu, AtsushiSolar Energy Materials & Solar Cells (2011), 95 (8), 2352-2356CODEN: SEMCEQ; ISSN:0927-0248. (Elsevier B.V.)The correlation among the elec., optical and structural properties of Ag thin films was investigated. Low-emissivity (low-e) coatings consisting of glass/ZnO/Ag were deposited by magnetron sputtering. The ZnO thin films were deposited under various oxygen gas pressures to vary the property of Ag thin films deposited on them. When the ZnO thin films were deposited in low oxygen gas pressure, the Ag thin films deposited on the ZnO thin films exhibited low resistivity and smooth surface. Besides, it was found that the low-emissivity coatings with low visible and near IR light absorbance were obtained using the low-resistive and smooth Ag thin films. It was concluded from the results that the light absorbance became low with decreasing the resistivity of Ag thin films in accordance with Drude's theory in the case where the Ag thin films exhibited sufficiently smooth surface. Furthermore, it can be considered that the surface plasmon polariton of Ag thin films had an influence on the optical property when their surface became rough. The optical absorbance of the low-e coatings should be detd. as the result of the competition between two factors: resistivity and surface roughness of Ag thin films.
- 61Granqvist, C. G. Transparent Conductors as Solar Energy Materials: A Panoramic Review. Sol. Energy Mater. Sol. Cells 2007, 91, 1529– 1598, DOI: 10.1016/j.solmat.2007.04.031Google Scholar61https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXpt1ylu78%253D&md5=93b43c5af274d397b06367f0e27e0b17Transparent conductors as solar energy materials: A panoramic reviewGranqvist, Claes G.Solar Energy Materials & Solar Cells (2007), 91 (17), 1529-1598CODEN: SEMCEQ; ISSN:0927-0248. (Elsevier B.V.)A review. Transparent conductors (TCs) have a multitude of applications for solar energy utilization and for energy savings, esp. in buildings. The largest of these applications, in terms of area, make use of the fact that the TCs have low IR emittance and hence can be used to improve the thermal properties of modern fenestration. Depending on whether the TCs are reflecting or not in the near IR pertinent to solar irradn., the TCs can serve in "solar control" or "low-emittance" windows. Other applications rely on the elec. cond. of the TCs, which make them useful as current collectors in solar cells and for inserting and extg. elec. charge in electrochromic "smart windows" capable of combining energy efficiency and indoor comfort in buildings. This Review takes a "panoramic" view on TCs and discusses their properties from the perspective of the radiative properties in our ambience. This approach leads naturally to considerations of spectral selectivity, angular selectivity, and temporal variability of TCs, as covered in three subsequent sections. The spectrally selective materials are thin films based on metals (normally gold or titanium nitride) or wide band gap semiconductors with heavy doping (normally based on indium, tin, or zinc). Their applications to energy-efficient windows are covered in detail, exptl. as well as theor., and briefer discussions are given applications to solar cells and solar collectors. Photocatalytic properties and super-hydrophilicity are touched upon. Angular selective TCs, for which the angular properties are caused by inclined columnar nanostructures, are then covered. A discussion of TC-like materials with thermochromic and electrochromic properties follows in the final part. Detailed treatments are given for thermochromic materials based on vanadium dioxide and for electrochromic multi-layer structures (incorporating TCs as essential components). The ref. list is extensive and aims at giving an easy entrance to the many varied aspects of TCs.
- 62Butt, M. A.; Fomchenkov, S. A.; Kazanskiy, N. L.; Ullah, A.; Ali, R. Z.; Habib, M. Infrared Reflective Coatings for Building and Automobile Glass Windows for Heat Protection. In Proceedings of SPIE Optical Technologies in Telecommunications; International Society for Optics and Photonics, Samara, Russian Federation, April 2017; 2016, Vol. 10342.Google ScholarThere is no corresponding record for this reference.
- 63Doremus, R. H. Optical Properties of Thin Metallic Films in Island Form. J. Appl. Phys. 1966, 37, 2775– 2781, DOI: 10.1063/1.1782121Google ScholarThere is no corresponding record for this reference.
- 64Mattinen, M.; Hämäläinen, J.; Gao, F.; Jalkanen, P.; Mizohata, K.; Räisänen, J.; Puurunen, R. L.; Ritala, M.; Leskelä, M. Nucleation and Conformality of Iridium and Iridium Oxide Thin Films Grown by Atomic Layer Deposition. Langmuir 2016, 32, 10559– 10569, DOI: 10.1021/acs.langmuir.6b03007Google Scholar64https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFOkt7nM&md5=e1c641926c33868f722e69ad8098bf1aNucleation and Conformality of Iridium and Iridium Oxide Thin Films Grown by Atomic Layer DepositionMattinen, Miika; Hamalainen, Jani; Gao, Feng; Jalkanen, Pasi; Mizohata, Kenichiro; Raisanen, Jyrki; Puurunen, Riikka L.; Ritala, Mikko; Leskela, MarkkuLangmuir (2016), 32 (41), 10559-10569CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Nucleation and conformality are important issues, when depositing thin films for demanding applications. Iridium and iridium dioxide (IrO2) films were deposited by at. layer deposition (ALD), using five different processes. Different reactants, namely, O2, air, consecutive O2 and H2 (O2 + H2), and consecutive O3 and H2 (O3 + H2) pulses were used with iridium acetylacetonate [Ir(acac)3] to deposit Ir, while IrO2 was deposited using Ir(acac)3 and O3. Nucleation was studied using a combination of methods for film thickness and morphol. evaluation. In conformality studies, microscopic lateral high-aspect-ratio (LHAR) test structures, specifically designed for accurate and versatile conformality testing of ALD films, were used. The order of nucleation, from the fastest to the slowest, was O2 + H2 > air ≈ O2 > O3 > O3 + H2, whereas the order of conformality, from the best to the worst, was O3 + H2 > O2 + H2 > O2 > O3. In the O3 process, a change in film compn. from IrO2 to metallic Ir was seen inside the LHAR structures. Compared to the previous reports on ALD of platinum-group metals, most of the studied processes showed good to excellent results.
- 65Kim, K.; Yong, K. Highly Conformal Cu Thin-Film Growth by Low-Temperature Pulsed MOCVD. Electrochem. Solid-State Lett. 2003, 6, C106– C108, DOI: 10.1149/1.1587071Google Scholar65https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXkvFyitLk%253D&md5=d30b60da277fa4cf62e5ab4e38a4583fHighly Conformal Cu Thin-Film Growth by Low-Temperature Pulsed MOCVDKim, Kwansoo; Yong, KijungElectrochemical and Solid-State Letters (2003), 6 (8), C106-C108CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)Highly conformal Cu thin films were deposited on the SiO2 trench substrate with an aspect ratio of 10 by pulsed metalorg. CVD (MOCVD) using cycles of the alternate supply of (hexafluoroacetylacetonate)Cu(I)(3,3-dimethyl-1-butene) [(hfac)Cu(DMB)] pulse and Ar purge gas. The film was 75 nm thick with a good step coverage. The growth temp. was 70° and the growth rate was 0.75-1.1 Å/cycle depending on the (hfac)Cu(DMB) pulse duration of 5-10 s. X-ray diffraction patterns of the Cu films showed a preferential crystallog. orientation of (111) plane of Cu. The impurities of C and F atom in the Cu films were below detection limits and only O atom was detected <3 av. atom% by XPS.
- 66Kikuchi, H.; Yamada, Y.; Ali, A. M.; Liang, J.; Fukushima, T.; Tanaka, T.; Koyanagi, M. Tungsten Through-Silicon via Technology for Three-Dimensional LSIs. Jpn. J. Appl. Phys. 2008, 47, 2801– 2806, DOI: 10.1143/JJAP.47.2801Google Scholar66https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXlsl2lsrk%253D&md5=1cb9565a20a60c6f48291de88ce4d535Tungsten through-silicon via technology for three-dimensional LSIsKikuchi, Hirokazu; Yamada, Yusuke; Ali, Atif Mossad; Liang, Jun; Fukushima, Takafumi; Tanaka, Tetsu; Koyanagi, MitsumasaJapanese Journal of Applied Physics (2008), 47 (4, Pt. 2), 2801-2806CODEN: JJAPB6 ISSN:. (Japan Society of Applied Physics)Tungsten through-silicon via (W-TSV) technol. is investigated for the fabrication of three-dimensional (3D) LSI chips having low-resistive TSVs with a width less than 3 μm. In the 3D integration technol., completed two-dimensional (2D) LSI chips including metal-oxide-semiconductor field-effect transistors (MOSFETs) and metal wirings are vertically stacked through a no. of short vertical interconnections called TSV with lengths ranging from several microns to several tens of microns. The W-TSV technol. is mainly divided into three low-temp. processes: deep-trench etching, dielec. layer formation, and filling with a conductive material. We successfully formed deep Si trenches through a 6-μm-thick SiO2 dielec. layer by the modified Bosch process. The depth of the resulting Si trenches with a dielec. layer is approx. 40 μm. A SiO2 layer was formed at the bottom and on the sidewall of the Si trenches by sub-atm. chem. vapor deposition (SACVD) method using tetraethylorthosilicate (TEOS) and O3. In addn., we succeeded in uniformly depositing a conformal W metal layer by time-modulated W-CVD method at 300°.
- 67Song, M.; Wang, D.; Peana, S.; Choudhury, S.; Nyga, P.; Kudyshev, Z. A.; Yu, H.; Boltasseva, A.; Shalaev, V. M.; Kildishev, A. V. Colors with Plasmonic Nanostructures: a Full-Spectrum Review. Appl. Phys. Rev. 2019, 6, 041308 DOI: 10.1063/1.5110051Google Scholar67https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitVCgu7%252FE&md5=b89cc47ab4efec652a7b753476566b01Colors with plasmonic nanostructures: A full-spectrum reviewSong, Maowen; Wang, Di; Peana, Samuel; Choudhury, Sajid; Nyga, Piotr; Kudyshev, Zhaxylyk A.; Yu, Honglin; Boltasseva, Alexandra; Shalaev, Vladimir M.; Kildishev, Alexander V.Applied Physics Reviews (2019), 6 (4), 041308CODEN: APRPG5; ISSN:1931-9401. (American Institute of Physics)Since ancient times, plasmonic structural coloring has inspired humanity; glassmakers achieved vibrant colors by doping glass with metal nanoparticles to craft beautiful objects such as the Roman Lycurgus cup and stained glass. These lovely color filtering effects are a consequence of the resonant coupling of light and free electrons in metal nanoparticles, known as surface plasmons. Thanks to the continuing improvement of nanofabrication technol., the dimensions of nanoparticles and structures can now be precisely engineered to form "optical nanoantennas," allowing for control of optical response at an unprecedented level. Recently, the field of plasmonic structural coloring has seen extensive growth. In this review, we provide an up-to-date overview of various plasmonic color filtering approaches and highlight their uses in a broad palette of applications. Various surface plasmon resonance modes employed in the plasmonic color filtering effect are discussed. We first review the development of the pioneering static plasmonic colors achieved with invariant optical nanoantennas and ambient environment, then we address a variety of emerging approaches that enable dynamic color tuning, erasing, and restoring. These dynamic color filters are capable of actively changing the filtered colors and carrying more color information states than the static systems. Thus, they open an avenue to high-d. data storage, information encryption, and plasmonic information processing. Finally, we discuss the challenges and future perspectives in this exciting research area. (c) 2019 American Institute of Physics.
- 68Gudur, A.; Ji, H.-F. Bio-Applications of Nanopillars. Front. Nanosci. Nanotechnol. 2016, 2, 1– 10Google ScholarThere is no corresponding record for this reference.
- 69Choudhury, B. D.; Casquel, R.; Bañuls, M. J.; Sanza, F. J.; Laguna, M. F.; Holgado, M.; Puchades, R.; Maquieira, A.; Barrios, C. A.; Anand, S. Silicon Nanopillar Arrays with SiO2 Overlayer for Biosensing Application. Opt. Mater. Express 2014, 4, 1345– 1354, DOI: 10.1364/OME.4.001345Google ScholarThere is no corresponding record for this reference.
- 70Dong, H.; Hinestroza, J. P. Metal Nanoparticles on Natural Cellulose Fibers: Electrostatic Assembly and In Situ Synthesis. ACS Appl. Mater. Interfaces 2009, 1, 797– 803, DOI: 10.1021/am800225jGoogle Scholar70https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXjvVegtbs%253D&md5=c00600a9b72728c3b9f25a387474cca8Metal Nanoparticles on Natural Cellulose Fibers: Electrostatic Assembly and In Situ SynthesisDong, Hong; Hinestroza, Juan P.ACS Applied Materials & Interfaces (2009), 1 (4), 797-803CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)The conformal deposition of metal nanoparticles (Au, Pd, and Pt) onto natural cellulose fibers using two chem. strategies is reported. The driving mechanism responsible for the high surface coverage of the substrates was identified as the electrostatic interactions between the pos. charged cellulose and the either neg. charged nanoparticles or neg. metal complex ions. The natural cellulose fibers were rendered cationic by grafting ammonium ions, using an epoxy substitution reaction, to the abundant hydroxyl groups present in cellulose mols. The first method involved the electrostatic assembly of citrate-stabilized metal nanoparticles directly onto the cationic surfaces of cellulose. The second method involved the adsorption of neg. metal complex ions onto the cationic cellulose followed by a redn. reaction. The attained metal nanoparticles bound with cellulose fibers were characterized by electron microscopy (TEM and SEM) and energy-dispersive X-ray spectroscopy (EDX). Both pathways generated metal nanoparticles with high packing densities on the cellulose substrates even when very dil. solns. of metal colloids or metal salts were used. Achieving high surface coverage with low-concn. precursor solns. may open an avenue for the prodn. of flexible catalytic mantles or highly functionalized textile substrates.
- 71Vaish, A.; Krueger, S.; Dimitriou, M.; Majkrzak, C.; Vanderah, D. J.; Chen, L.; Gawrisch, K. Enhancing the Platinum Atomic Layer Deposition Infiltration Depth Inside Anodic Alumina Nanoporous Membrane. J. Vac. Sci. Technol., A 2015, 33, 01A148 DOI: 10.1116/1.4904398Google ScholarThere is no corresponding record for this reference.
- 72Kariniemi, M.; Niinistö, J.; Vehkamäki, M.; Kemell, M.; Ritala, M.; Leskelä, M.; Putkonen, M. Conformality of Remote Plasma-Enhanced Atomic Layer Deposition Processes: An Experimental Study. J. Vac. Sci. Technol., A 2012, 30, 01A115 DOI: 10.1116/1.3659699Google ScholarThere is no corresponding record for this reference.
- 73Golrokhi, Z.; Chalker, S.; Sutcliffe, C. J.; Potter, R. J. Self-Limiting Atomic Layer Deposition of Conformal Nanostructured Silver Films. Appl. Surf. Sci. 2016, 364, 789– 797, DOI: 10.1016/j.apsusc.2015.12.127Google Scholar73https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitFSlt7rF&md5=2d1b5da6238d67a3302dcbea0647d41fSelf-limiting atomic layer deposition of conformal nanostructured silver filmsGolrokhi, Zahra; Chalker, Sophia; Sutcliffe, Christopher J.; Potter, Richard J.Applied Surface Science (2016), 364 (), 789-797CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)Here we develop a self-limiting at. layer deposition (ALD) process for the deposition of conformal metallic silver nanoparticle films. The films have been deposited using direct liq. injection ALD with ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) and propan-1-ol. An ALD temp. window between 123 and 128 °C is identified and within this range self-limiting growth is confirmed with a mass deposition rate of ∼17.5 ng/cm2/cycle. The effects of temp., precursor dose, co-reactant dose and cycle no. on the deposition rate and on the properties of the films have been systematically investigated. Under self-limiting conditions, films are metallic silver with a nano-textured surface topog. and nanoparticle size is dependent on the no. of ALD cycles. The ALD reaction mechanisms have been elucidated using in-situ quartz crystal microbalance (QCM) measurements, showing chemisorption of the silver precursor, followed by heterogeneous catalytic dehydrogenation of the alc. to form metallic silver and an aldehyde.
- 74Ylilammi, M.; Ylivaara, O. M. E.; Puurunen, R. L. Modeling Growth Kinetics of Thin Films Made by Atomic Layer Deposition in Lateral High-Aspect-Ratio Structures. J. Appl. Phys. 2018, 123, 205301, DOI: 10.1063/1.5028178Google Scholar74https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXpvVOisLw%253D&md5=15aedcfe4186f70f42131442ac9f7da9Modeling growth kinetics of thin films made by atomic layer deposition in lateral high-aspect-ratio structuresYlilammi, Markku; Ylivaara, Oili M. E.; Puurunen, Riikka L.Journal of Applied Physics (Melville, NY, United States) (2018), 123 (20), 205301/1-205301/8CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The conformality of thin films grown by at. layer deposition (ALD) is studied using all-silicon test structures with long narrow lateral channels. A diffusion model, developed in this work, is used for studying the propagation of ALD growth in narrow channels. The diffusion model takes into account the gas transportation at low pressures, the dynamic Langmuir adsorption model for the film growth and the effect of channel narrowing due to film growth. The film growth is calcd. by solving the diffusion equation with surface reactions. An efficient analytic approx. soln. of the diffusion equation is developed for fitting the model to the measured thickness profile. The fitting gives the equil. const. of adsorption and the sticking coeff. This model and Gordon's plug flow model are compared. The simulations predict the exptl. measurement results quite well for Al2O3 and TiO2 ALD processes. (c) 2018 American Institute of Physics.
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Abstract
Figure 1
Figure 1. Scanning electron micrographs of Ag thin films on glass substrates (a) as-deposited and (b) post-treated films. The EDS equivalent thickness is 24 ± 2 nm in both cases. The values shown in the middle of the images correspond to the sheet resistance of the Ag layer.
Figure 2
Figure 2. Morphological properties of Ag thin films. (a, b) Atomic force micrographs of Ag thin films on silicon substrates (a) as-deposited and (b) post-treated films. The EDS equivalent thickness is 40 ± 2 nm in both cases. The values shown in the middle of the images correspond to the rms roughness of the Ag layer. (c) SEM cross section of the as-deposited Ag thin film on a silicon substrate. The value shown in the middle of the image corresponds to the EDS equivalent thickness of the Ag layer.
Figure 3
Figure 3. (a, b) Elemental composition (in at.%) of Ag thin films synthetized on a silicon substrate using the new process (EDS equivalent thickness of 26 ± 2 nm) measured by XPS before (etching time, 0 s) and after Ar sputtering (two different etching times, 140 and 280 s). (a) As-deposited and (b) post-treated Ag thin films. (c) Modified Auger parameter (α′) of Ag for different etching times for as-deposited (red squares) and post-treated (black disks) layers. The blue line corresponds to a reference Ag foil. The error bars correspond to the experimental error linked to the spectrum acquisition step size. (d) X-ray diffraction spectrogram of Ag thin films synthetized on a silicon substrate (EDS equivalent thickness of 61 ± 3 nm) corresponding to as-deposited (in red) and post-treated (in black) films. The inset corresponds to the crystallite size extracted from (111), (200), (220), and (311) diffraction peaks of as-deposited (in red) and post-treated (in black) films.
Figure 4
Figure 4. Sheet resistance as a function of EDS equivalent thickness of Ag thin films on glass substrates. The data have been referred for the as-deposited (red triangle symbols) and post-treated (black square symbols) films. The blue spots have been obtained by a standard ALD process, following our previous work. (26) The green curve has been plotted as a reference for the Ag thin film deposited by magnetron sputtering, following the publication of Hauder et al. (3)
Figure 5
Figure 5. Optical properties of Ag thin films on glass substrates and application as infrared-reflective (IRR) coating. (a) Transmittance (%T in solid lines), reflectance (%R in dashed lines), and calculated absorbance (%A = 100 – %R – %T in dash-dot lines) spectra as a function of light wavelength corresponding to the as-deposited (in red) and post-treated (in black) Ag thin layer. The EDS equivalent thickness is 42 ± 2 nm. (b) Picture of a bent glass substrate of 10 cm × 10 cm coated with a 45 nm (thickness determined by ellipsometry) AZO and targeted 40 nm Ag thin film. (c) Transmittance (%T in red) and reflectance (%R in blue) spectra as a function of light wavelength for an IRR stack based on a Ag thin layer (targeted thickness below 20 nm) embedded in the AZO matrix (45 nm for each layer). The inset represents a scheme of the multilayer stack. Plain lines correspond to the measured spectra, and dashed lines correspond to the calculated spectra using, for the Ag film, the optical constants represented in panel (d) and a thickness of 12 nm. (d) Real part (ε1) and imaginary part (ε2) of the dielectric constant used for modelling the silver film in the calculation in panel (c). The model used for simulating the experimental data (plain line) is compared to the optical constants for the evaporated Ag thin film determined by Johnson and Christy. (57) (e) Picture of the same kind of stack as panel (c) deposited on a two-sided-bent glass substrate of 10 cm × 10 cm. Glass thickness is 2 mm.
Figure 6
Figure 6. Degree of conformality of Ag thin films on 3D structures. (a, b) Scheme of an expected thin film deposition on a lateral high aspect ratio structure by the (a) line-of-sight technique and (b) conformal technique. (c) Low-magnification SEM cross section of post-treated Ag thin films synthetized on an LHAR structure (AR of 100). (d, e) High-magnification SEM cross sections of the structure shown in panel (c), taken (d) at the entrance and (e) at the back of the LHAR structure. (f, g) SEM images of post-treated Ag thin films grown on the sidewalls of a micro via hole (zoomed in image in panel (g)). (h) SEM image of a Ag thin layer after PT deposited on silicon pillars.
Figure 7
Figure 7. (a) Thickness profiles measured on an LHAR structure with an AR of 10,000 (w of 100 μm, l of 5000 μm, and h of 500 nm) of Ag films deposited with the standard PE-ALD process (blue) and with our novel approach before (red) and after (black) plasma post-treatment. The thickness has been measured by EDS after removing the top membrane of the LHAR structure. The fits are an exponential dependence for the standard PE-ALD method and a diffusion law for the novel approach (see main text). (b–g) Scanning electron micrographs (top view) of Ag thin films (b–d) before and (e–g) after the post-treatment step and synthetized in the same structure as panel (a) at a penetration depth (PD) of (b–e) 0, (c–f) 9, and (d–g) 20 μm. The values on the middle of the images correspond to the EDS equivalent thickness of the Ag layer.
References
This article references 74 other publications.
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- 2Hagen, D. J.; Pemble, M. E.; Karppinen, M. Atomic Layer Deposition of Metals: Precursors and Film Growth. Appl. Phys. Rev. 2019, 6, 041309 DOI: 10.1063/1.50877592https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitFansr7O&md5=f3c610893e495981ef5668891380dd7eAtomic layer deposition of metals: Precursors and film growthHagen, D. J.; Pemble, M. E.; Karppinen, M.Applied Physics Reviews (2019), 6 (4), 041309/1-041309/63CODEN: APRPG5; ISSN:1931-9401. (American Institute of Physics)A review. The coating of complex three-dimensional structures with ultrathin metal films is of great interest for current tech. applications, particularly in microelectronics, as well as for basic research on, for example, photonics or spintronics. While at. layer deposition (ALD) has become a well-established fabrication method for thin oxide films on such geometries, attempts to develop ALD processes for elemental metal films have met with only mixed success. This can be understood by the lack of suitable precursors for many metals, the difficulty in reducing the metal cations to the metallic state, and the nature of metals as such, in particular their tendency to agglomerate to isolated islands. In this review, we will discuss these three challenges in detail for the example of Cu, for which ALD has been studied extensively due to its importance for microelectronic fabrication processes. Moreover, we give a comprehensive overview over metal ALD, ranging from a short summary of the early research on the ALD of the platinoid metals, which has meanwhile become an established technol., to very recent developments that target the ALD of electropos. metals. Finally, we discuss the most important applications of metal ALD. (c) 2019 American Institute of Physics.
- 3Hauder, M.; Gstöttner, J.; Hansch, W.; Schmitt-Landsiedel, D. Scaling Properties and Electromigration Resistance of Sputtered Ag Metallization Lines. Appl. Phys. Lett. 2001, 78, 838– 840, DOI: 10.1063/1.13458013https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXotlOktA%253D%253D&md5=4fded9be092b278a052ab1b662b3c327Scaling properties and electromigration resistance of sputtered Ag metallization linesHauder, M.; Gstottner, J.; Hansch, W.; Schmitt-Landsiedel, D.Applied Physics Letters (2001), 78 (6), 838-840CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Resistivity and electromigration were investigated for thin sputtered Ag films and microstructured Ag lines. Resistivities of thin films were found to be lower compared to copper and follow the prediction of the size effect. Microstructured Ag lines show a high electromigration resistance at accelerated stress measurements. Considering Joule heating of the lines, the activation energy for electromigration was found to be 0.58 eV. The extrapolated median lifetime of Ag lines was found to be similar or higher than for Cu lines.
- 4Gao, L.; Härter, P.; Linsmeier, C.; Gstöttner, J.; Emling, R.; Schmitt-Landsiedel, D. Metalorganic Chemical Vapor Deposition of Silver Thin Films for Future Interconnects by Direct Liquid Injection System. Mater. Sci. Semicond. Process. 2004, 7, 331– 335, DOI: 10.1016/j.mssp.2004.09.1284https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXpvVelu70%253D&md5=463e309fc00d9f32b365958f21337089Metalorganic chemical vapor deposition of silver thin films for future interconnects by direct liquid injection systemGao, L.; Haerter, P.; Linsmeier, Ch.; Gstoettner, J.; Emling, R.; Schmitt-Landsiedel, D.Materials Science in Semiconductor Processing (2004), 7 (4-6), 331-335CODEN: MSSPFQ; ISSN:1369-8001. (Elsevier Ltd.)Deposition of Ag films by direct liq. injection-metal org. chem. vapor deposition (DLI-MOCVD) was chosen because this prepn. method allows precise control of precursor flow and prevents early decompn. of the precursor as compared to the bubbler-delivery. Silver(I)-2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionato-triethylphosphine [Ag(fod)(PEt3)] as the precursor for Ag CVD was studied, which is liq. at 30°C. Ag films were grown on different substrates of SiO2/Si and TiN/Si. Argon and nitrogen/hydrogen carrier gas was used in a cold wall reactor at a pressure of 50-500 Pa with deposition temp. ranging between 220°C and 350°C. Ag films deposited on a TiN/Si diffusion barrier layer have favorable properties over films deposited on SiO2/Si substrate. At lower temp. (220°C), film growth is essentially reaction-limited on SiO2 substrate. Significant dependence of the surface morphol. on the deposition conditions exists in our expts. According to XPS anal. pure Ag films are deposited by DLI-MOCVD at 250°C by using argon as carrier gas.
- 5Amusan, A. A.; Kalkofen, B.; Gargouri, H.; Wandel, K.; Pinnow, C.; Lisker, M.; Burte, E. P. Ag Films Grown by Remote Plasma Enhanced Atomic Layer Deposition on Different Substrates. J. Vac. Sci. Technol., A 2016, 34, 01A126 DOI: 10.1116/1.4936221There is no corresponding record for this reference.
- 6Szczyrbowski, J.; Dietrich, A.; Hartig, K. Evaluation and Control of the Properties of Thin Sputtered Silver Films for Spectrally Selective Coatings. Sol. Energy Mater. 1987, 16, 103– 111, DOI: 10.1016/0165-1633(87)90012-86https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXlt1entbk%253D&md5=3fc15fc1f13ff268f769c2d8b9e8092dEvaluation and control of the properties of thin sputtered silver films for spectrally selective coatingsSzczyrbowski, J.; Dietrich, A.; Hartig, K.Solar Energy Materials (1987), 16 (1-3), 103-11CODEN: SOEMDH; ISSN:0165-1633.The influence of the deposition parameters on the elec. and optical properties of very thin Ag films prepd. by magnetron sputtering was studied. To evaluate the film properties, a method was used, which is based on simple optical transmission measurements. The results show that the specific resistivity, the plasma energy and the optical resistivity of films below 30 nm thickness are very sensitive to such deposition parameters as cathode power d. The variations in the optical and elec. properties are related to the d. of the sputtered films.
- 7Boccas, M.; Vucina, T.; Araya, C.; Vera, E.; Ahhee, C. Protected-Silver Coatings for the 8-m Gemini Telescope Mirrors. Thin Solid Films 2006, 502, 275– 280, DOI: 10.1016/j.tsf.2005.07.2957https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XhslyjtLc%253D&md5=bcc72bb685f711f7fa9ec2f68561788aProtected-silver coatings for the 8-m Gemini telescope mirrorsBoccas, M.; Vucina, T.; Araya, C.; Vera, E.; Ahhee, C.Thin Solid Films (2006), 502 (1-2), 275-280CODEN: THSFAP; ISSN:0040-6090. (Elsevier B.V.)The twin 8-m diam. Gemini telescopes were designed to use silver-based coatings on the mirrors in order to provide very high reflectivity and ultra-low emissivity for optimal IR performance. A feasibility study provided both techniques and recipes to apply these thin films, and showed that a reflectivity of 99.1% at 10 μm was achievable. We have now produced bare and protected silver sputtered films in our coating plants and conducted environmental testing, both accelerated and in real-life conditions, to assess the durability in an observatory environment. We have also already applied, for the first time ever, protected-silver coatings on the main optical elements of a large telescope. We report here the performance of the films, the challenges to coat a 50 m2 primary mirror (M1) and our plans for coating maintenance.
- 8Butler, M. A.; Ricco, A. J. Chemisorption-Induced Reflectivity Changes in Optically Thin Silver Films. Appl. Phys. Lett. 1988, 53, 1471, DOI: 10.1063/1.1004648https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1cXmtlOku7g%253D&md5=c8be4378ce03f5d8a48b7615b2d7357eChemisorption-induced reflectivity changes in optically thin silver filmsButler, M. A.; Ricco, A. J.Applied Physics Letters (1988), 53 (16), 1471-3CODEN: APPLAB; ISSN:0003-6951.The reflectivity of an optically thin metal film was used to investigate its interactions with chemisorbed mols. Reflectivity decreases for semitransparent, thin (50-250 Å) Ag films vacuum evapd. on the end of multimode optical fibers were obsd. at 860 nm during chemisorption of various mols. The magnitude of the decrease depends on the nature of the mol./Ag interaction. The dependence of this effect on film thickness is consistent with changes in the optical thickness as a result of chemisorption. This effect may lead to the development of new chem. sensors.
- 9Guo, S.; Wang, E. Noble Metal Nanomaterials: Controllable Synthesis and Application in Fuel Cells and Analytical Sensors. Nano Today 2011, 6, 240– 264, DOI: 10.1016/j.nantod.2011.04.0079https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpvVWqtbg%253D&md5=f2f1f12222c748f2c2c07f311ae54411Noble metal nanomaterials: controllable synthesis and application in fuel cells and analytical sensorsGuo, Shaojun; Wang, ErkangNano Today (2011), 6 (3), 240-264CODEN: NTAOCG; ISSN:1748-0132. (Elsevier Ltd.)A review. Nobel metal nanomaterials (NMNs) with interesting phys. and chem. properties are ideal building blocks for engineering and tailoring nanoscale structures for specific technol. applications. Particularly, effectively controlling the size, shape, architecture, compn., hybrid and microstructure of NMNs plays an important role on revealing their new or enhanced functions and application potentials such as fuel cell and anal. sensors. This review article focuses on recent advances on controllable synthesis and fuel cell and sensing applications of NMNs. First, recent contributions on developing a wet-chem. approach for the controllable synthesis of noble metal nanomaterials with a rich variety of shapes, e.g. single-component Pt, Pd, Ag and Au nanomaterials, multi-component core/shell, intermetallic or alloyed nanomaterials, metal fluorescent nanoclusters and metal nanoparticles-based hybrid nanomaterials, are summarized. Then diversified approaches to different types of NMNs-based nanoelectrocatalysts with the aim to enhance their activity and durability for fuel cell reactions are outlined. The review next introduces some exciting push in the use of NMNs as enhanced materials or reporters or labels for developing new anal. sensors including electrochem., colorimetric and fluorescent sensors. Finally, we conclude with a look at the future challenges and prospects of the development of NMNs.
- 10Piedade, A. P.; Vieira, M. T.; Martins, A.; Silva, F. In Vitro Behaviour of Nanocrystalline Silver-Sputtered Thin Films. Nanotechnology 2007, 18, 105103, DOI: 10.1088/0957-4484/18/10/10510310https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkvFSitLc%253D&md5=fdf78c354ded761fa9a961a5523bb169In vitro behaviour of nanocrystalline silver-sputtered thin filmsPiedade, A. P.; Vieira, M. T.; Martins, A.; Silva, F.Nanotechnology (2007), 18 (10), 105103/1-105103/5CODEN: NNOTER; ISSN:0957-4484. (Institute of Physics Publishing)Silver thin films were deposited with different preferential orientations and special attention was paid to the bioreactivity of the surfaces. The study was essentially focused on the evaluation of the films by x-ray diffraction (XRD), at. force microscopy (AFM), high-resoln. transmission electron microscopy (HRTEM), electron probe microanal. (EPMA) and contact angle measurements. The deposited thin films were characterized before and after immersion in S-enriched simulated human plasma to est. the influence of the preferential crystallog. orientation on the in vitro behavior. Silver thin films with and without (111) preferential crystallog. orientation were deposited by r.f. magnetron sputtering to yield nanocryst. coatings, high compact structures, very hydrophobic surfaces and low roughness. These properties reduce the chemisorption of reactive species onto the film surface. The in vitro tests indicate that silver thin films can be used as coatings for biomaterials applications.
- 11Guske, J. T.; Brown, J.; Welsh, A.; Franzen, S. Infrared Surface Plasmon Resonance of AZO-Ag-AZO Sandwich Thin Films. Opt. Express 2012, 20, 23215– 23226, DOI: 10.1364/OE.20.02321511https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsFCisLfE&md5=2fce4f2e2b91798937f8876ada3a8923Infrared surface plasmon resonance of AZO-Ag-AZO sandwich thin filmsGuske, Joshua T.; Brown, Jeff; Welsh, Alex; Franzen, StefanOptics Express (2012), 20 (21), 23215-23226CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)Near-IR surface plasmon resonance (SPR) spectra were collected of thin multilayer films of aluminum-doped zinc oxide (AZO)/silver (Ag)/AZO on BK-7 glass in the Kretschmann configuration in air, with the silver layer thickness varying from 5 nm to 50 nm. The SPR results were interpreted by modeling the reflectance with a five-layer transfer-matrix method, with the aid of a simplex algorithm. The model indicated that the Ag plasma frequency was significantly higher than the bulk value, possibly due to Schottky effect charge transfer from the AZO to the Ag layer. Continuous silver films were made as thin as 10 nm, indicating an inhibition of metal island formation for Ag deposited on AZO.
- 12West, G. T.; Kelly, P. J.; Bradley, J. W. A Comparison of Thin Silver Films Grown Onto Zinc Oxide via Conventional Magnetron Sputtering and HiPIMS Deposition. IEEE Trans. Plasma Sci. 2010, 38, 3057– 3061, DOI: 10.1109/TPS.2010.206658012https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhs1WrsbfP&md5=552ae82c7daa8bcb02369b47dc5586bdA comparison of thin silver films grown onto zinc oxide via conventional magnetron sputtering and HiPIMS depositionWest, G. T.; Kelly, P. J.; Bradley, J. W.IEEE Transactions on Plasma Science (2010), 38 (11, Pt. 1), 3057-3061CODEN: ITPSBD; ISSN:0093-3813. (Institute of Electrical and Electronics Engineers)Silver coatings are commonly deposited via dc magnetron sputtering for use in a variety of applications that require high transparency to visible light and good elec. cond., including, for example, low-emissivity coatings. The films need to be fully dense in order to achieve the correct optical and elec. properties, although the typical growth mechanism for silver films is by the nucleation and coalescence of islandlike structures that can result in the generation of voids within the coating and uneven surface topog. As a consequence, in order to achieve acceptable elec. properties, the optical transparency of the silver coating is often compromised due to the excessive film thicknesses required for continuous elec. conductive layers. Conventional methods used to enhance the adatom mobility, hence increasing the d. of the coatings, include the application of an elec. bias to the substrate or substrate heating, both of which can be problematic for large-area dielec. substrates such as float glass or polymer web. One alternative is the prodn. of a coating using a deposition flux with a high fraction of ionization. This can be achieved via high-power impulse magnetron sputtering (HiPIMS), leading to an enhanced delivery of energy to the adatoms via recombination at the substrate surface. Thin films of silver were deposited onto zinc oxide-coated glass substrates via continuous dc and pulsed-dc magnetron sputtering and also via HiPIMS at the same time-averaged power in order to compare the structure and growth mechanisms via techniques, including AFM, XRD, and Hall-effect measurements for the elec. characterization.
- 13Banzai, K.; Naka, S.; Okada, H. MoO3/Ag/MoO3 Anode for Organic Light-Emitting Diodes and its Carrier Injection Property. Jpn. J. Appl. Phys. 2015, 54, 054101 DOI: 10.7567/JJAP.54.054101There is no corresponding record for this reference.
- 14Gu, D.; Zhang, C.; Wu, Y.-K.; Guo, L. J. Ultrasmooth and Thermally Stable Silver-Based Thin Films with Subnanometer Roughness by Aluminum Doping. ACS Nano 2014, 8, 10343– 10351, DOI: 10.1021/nn503577c14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFamsL7E&md5=a8b714c4bec79c15b6d5dfc1ad5289bcUltrasmooth and thermally stable silver-based thin films with subnanometer roughness by aluminum dopingGu, Deen; Zhang, Cheng; Wu, Yi-Kuei; Guo, L. JayACS Nano (2014), 8 (10), 10343-10351CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Rough surface and poor stability of ultrathin Ag films limit their applications in nanophotonic and optoelectronic devices. Here, we report an approach for fabricating ultrasmooth and thermally stable Ag-based thin films on SiO2/Si substrates by Al-doping. The effect of Al-doping on the surface morphol. and stability of ultrathin Ag films at room temp. and elevated temp. was investigated. The 15 nm Al-doped Ag films with an Al at. concn. of 4% have a root-mean-square roughness as low as 0.4 nm. The smooth surface morphol. is maintained even after 300°C annealing in N2. Al-doping enhances the nuclei d. of films. Moreover, a capping layer spontaneously formed over the Al-doped Ag films restrains the surface diffusion and mass transportation of Ag atoms. Therefore, Al-doping induces ultrathin Ag films with highly stable and ultrasmooth surface morphol.
- 15Huang, J.; Liu, X.; Lu, Y.; Zhou, Y.; Xu, J.; Li, J.; Wang, H.; Fang, J.; Yang, Y.; Wang, W.; Tan, R.; Song, W. Seed-Layer-Free Growth of Ultra-Thin Ag Transparent Conductive Films Imparts Flexibility to Polymer Solar Cells. Sol. Energy Mater. Sol. Cells 2018, 184, 73– 81, DOI: 10.1016/j.solmat.2018.04.00215https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXptlSht7Y%253D&md5=215222b18dae9a90dd2b355b7a386271Seed-layer-free growth of ultra-thin Ag transparent conductive films imparts flexibility to polymer solar cellsHuang, Jinhua; Liu, Xiaohui; Lu, Yuehui; Zhou, Yuhong; Xu, Junjun; Li, Jia; Wang, Haiqiao; Fang, Junfeng; Yang, Ye; Wang, Weiyan; Tan, Ruiqin; Song, WeijieSolar Energy Materials & Solar Cells (2018), 184 (), 73-81CODEN: SEMCEQ; ISSN:0927-0248. (Elsevier B.V.)In this work, by introducing Cu dopant, ultra-thin Ag transparent conductive films were prepd. on glass and PET substrates without seed layers. The percolation threshold thickness for the Cu doped Ag thin films was as low as 6nm with a RMS roughness only 0.19nm. The prepd. 6nm Cu doped Ag thin films, Ag(Cu), had a transmittance of 80% at 550nm and a sheet resistance of 14.1Ωsq-1. The Ag(Cu) thin films revealed excellent thermal, chem., and mech. stability. Flexible polymer solar cells using the Ag(Cu) electrode reached a convert efficiency of 7.53% with a very thin PTB7-Th:PC71BM active layer. The proposed ultra-thin alloy transparent conductive films are ease of fabrication and beneficial to light harvesting, which are promising for large-area applications in flexible photovoltaics.
- 16Yang, Y.; Song, W.; Ding, L. Dielectric/Ultrathin Metal/Dielectric Structured Transparent Conducting Films for Flexible Electronics. Sci. Bull. 2020, 1324, DOI: 10.1016/j.scib.2020.04.02416https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhsFSisrfJ&md5=da3d2c95c075ada8187dd78e3f884934Dielectric/ultrathin metal/dielectric structured transparent conducting films for flexible electronicsYang, Ye; Song, Weijie; Ding, LimingScience Bulletin (2020), 65 (16), 1324-1326CODEN: SBCUA5; ISSN:2095-9281. (Elsevier B.V.)To be compatible with future new flexible electronics. The dielec./ultrathin metal/dielec. structured with long-term chem. stability, controllable surface chem. state (e.g., hydrophobic or hydrophilic)and adjustable work function and its more sophisticated integration in device should be further developed.
- 17Bahlawane, N.; Premkumar, P. A.; Brechling, A.; Reiss, G.; Kohse-Höinghaus, K. Alcohol-Assisted CVD of Silver Using Commercially Available Precursors. Chem. Vap. Deposition 2007, 13, 401– 407, DOI: 10.1002/cvde.20070661017https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtVWnu77P&md5=b1cf7632c9c9530260660aa35616ece1Alcohol-assisted CVD of silver using commercially available precursorsBahlawane, Naoufal; Premkumar, Peter Antony; Brechling, Armin; Reiss, Guenter; Kohse-Hoeinghaus, KatharinaChemical Vapor Deposition (2007), 13 (8), 401-407CODEN: CVDEFX; ISSN:0948-1907. (Wiley-VCH Verlag GmbH & Co. KGaA)A novel chem. approach was demonstrated for the growth of high-quality, Ag films by CVD. This concept relies on the catalytic reactivity of cationic Ag, and of Ag surfaces with alcs. This leads to high-purity films using either state-of-the-art precursors or Ag salts that were not yet considered as CVD precursors. The occurrence of the catalytic oxidative-dehydrogenation of alcs., considered as the driving force in this process, was shown by in-situ mass spectrometry (MS). Films of fcc.-Ag with ρ ≤ 2 μΩ cm were grown without any noticeable contamination. Ag(hfac)COD leads to the growth of a (111) highly orientated film on glass at a rate of 1.66 nm min-1, while polycryst. films are grown at a rate of 18.5 nm min-1 using AgNO3.
- 18Niskanen, A.; Hatanpää, T.; Arstila, K.; Leskelä, M.; Ritala, M. Radical-Enhanced Atomic Layer Deposition of Silver Thin Films Using Phosphine-Adducted Silver Carboxylates. Chem. Vap. Deposition 2007, 13, 408– 413, DOI: 10.1002/cvde.20060651918https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtVWnu77I&md5=171fe4da4eb1ffe070cdb7a6ec3e3e5aRadical-enhanced atomic layer deposition of silver thin films using phosphine-adducted silver carboxylatesNiskanen, Antti; Hatanpaa, Timo; Arstila, Kai; Leskela, Markku; Ritala, MikkoChemical Vapor Deposition (2007), 13 (8), 408-413CODEN: CVDEFX; ISSN:0948-1907. (Wiley-VCH Verlag GmbH & Co. KGaA)Silver films were deposited by radical-enhanced at. layer deposition using (2,2-dimethylpropionato)silver(I)triethylphosphine and hydrogen radicals. The silver precursor used is synthesized inhouse and characterized by using CHN elemental anal., IR spectroscopy, NMR, mass spectrometry and thermogravimetric anal./single DTA. The crystal structure of Ag(O2CtBu)(PEt3) is also solved. Trimeric units are revealed as the building blocks. The hydrogen radicals are produced by dissocg. mol. hydrogen with a microwave plasma discharge. The evapn. temp. of the silver precursor is 125°, and the film deposition temp. is 140°. The deposition is successful on glass and silicon, and the films are conformal. The satd. growth rate is 0.12 nm per cycle, with a 3 s silver precursor pulse and 5 s hydrogen radical pulse time. The overall cycle time is 14 s. The films are polycryst. and are visually mirror-like. The films contain 10 oxygen, 4.0 phosphorous, 1.0 carbon and 5.0 at.% hydrogen as impurities. Nevertheless, the films exhibit low elec. resistivity of only 6 μΩ-cm for a 40 nm thick film.
- 19Kariniemi, M.; Niinistö, J.; Hatanpää, T.; Kemell, M.; Sajavaara, T.; Ritala, M.; Leskelä, M. Plasma-Enhanced Atomic Layer Deposition of Silver Thin Films. Chem. Mater. 2011, 23, 2901– 2907, DOI: 10.1021/cm200402j19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXlvFClsLc%253D&md5=33e1707648ad5ee7d56f22e3456c1a4cPlasma-Enhanced Atomic Layer Deposition of Silver Thin FilmsKariniemi, Maarit; Niinisto, Jaakko; Hatanpaa, Timo; Kemell, Marianna; Sajavaara, Timo; Ritala, Mikko; Leskela, MarkkuChemistry of Materials (2011), 23 (11), 2901-2907CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)Thermal properties of various silver precursors known in the literature were evaluated in order to discover which precursor is the most suitable one for plasma-enhanced at. layer deposition (PEALD) of silver thin films. Ag(fod)(PEt3) (fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluorooctane-3,5-dionato) was found to be the best choice. Using Ag(fod)(PEt3) together with plasma-activated hydrogen, Ag thin films were deposited at growth temps. of 120-150°, and ALD-type saturative growth was achieved at 120-140°. At 120°, the growth rate was 0.03 nm per cycle. The plasma exposure time had also an effect on the growth rate: with shorter exposure times, the growth rate was lower over the whole deposition area. The films deposited at 120° contained relatively small amts. of impurities, but these still affected the elec. properties of the films. The resistivities were relatively low: about 20 nm thick films had a resistivity of 6-8 μΩ-cm. The morphol. and the crystal structure of the films were analyzed as well.
- 20Chalker, P. R.; Romani, S.; Marshall, P. A.; Rosseinsky, M. J.; Rushworth, S.; Williams, P. A. Liquid Injection Atomic Layer Deposition of Silver Nanoparticles. Nanotechnology 2010, 21, 405602, DOI: 10.1088/0957-4484/21/40/40560220https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsVygt7bO&md5=6fa609726efa7e0deb45646abf356103Liquid injection atomic layer deposition of silver nanoparticlesChalker, P. R.; Romani, S.; Marshall, P. A.; Rosseinsky, M. J.; Rushworth, S.; Williams, P. A.Nanotechnology (2010), 21 (40), 405602/1-405602/7CODEN: NNOTER; ISSN:1361-6528. (Institute of Physics Publishing)Silver nanoparticles are being developed for applications in plasmonics, catalysts and anal. methods, amongst others. Herein, we demonstrate the growth of silver nanoparticles using an at. layer deposition (ALD) process for the first time. The silver was deposited from pulses of the organometallic precursor (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I) (1,5-cyclooctadiene)) dissolved in a 0.1 M toluene soln. Catalytic oxidative dehydrogenation of the silver was achieved using intermittent pulses of propanol. The effect of substrate temp. on the size and distribution of nanoparticles has been investigated over the temp. range 110-150 °C.Transmission electron microscopy reveals that the nanoparticles consist of fcc., facetted silver crystallites. The localized surface plasmon modes of the nanoparticles have been investigated using electron energy loss spectroscopy mapping. The distributions of plasmons within the ALD nanoparticles are comparable to those grown by soln. methods. Both dipolar and quadrupolar resonant modes are obsd., which is consistent with previous discrete dipole approxn. models. Energy loss mapping of a loss feature at 8.1 eV reveals that it correlates with the bulk or vol. region of the silver nanoparticles investigated here.
- 21Mäkelä, M.; Hatanpää, T.; Mizohata, K.; Meinander, K.; Niinistö, J.; Räisänen, J.; Ritala, M.; Leskelä, M. Studies on Thermal Atomic Layer Deposition of Silver Thin Films. Chem. Mater. 2017, 29, 2040– 2045, DOI: 10.1021/acs.chemmater.6b0402921https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjtlCguro%253D&md5=a8e85af73ebb2debeea38bd15e5e5214Studies on Thermal Atomic Layer Deposition of Silver Thin FilmsMakela, Maarit; Hatanpaa, Timo; Mizohata, Kenichiro; Meinander, Kristoffer; Niinisto, Jaakko; Raisanen, Jyrki; Ritala, Mikko; Leskela, MarkkuChemistry of Materials (2017), 29 (5), 2040-2045CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)The growth of Ag thin films by thermal at. layer deposition (ALD) was studied. A com. Ag compd., Ag(fod) (PEt3), was applied with a reducing agent, di-Me amineborane (BH3(NHMe2)). A growth rate of 0.3 Å/cycle was measured for Ag at a deposition temp. of 110 °C. The purity of the particulate, polycryst. Ag thin films was studied with time-of-flight elastic recoil detection anal. (TOF-ERDA) and XPS. TOF-ERDA showed only small amts. of impurities in the film deposited at 110 °C, the main impurities being oxygen (1.6 at. %), hydrogen (0.8 at. %) and carbon (0.7 at. %). In addn. to the conventional ALD process, the idea of activation of the amineborate inside the ALD reactor was tested. A catalytic Ru surface was utilized to convert BH3(NHMe2) into possibly even more reducing species inside the reactor without contaminating the catalysts with a growing film.
- 22Golrokhi, Z.; Marshall, P. A.; Romani, S.; Rushworth, S.; Chalker, P. R.; Potter, R. J. The Influence of Tertiary Butyl Hydrazine as a Co-Reactant on the Atomic Layer Deposition of Silver. Appl. Surf. Sci. 2017, 399, 123– 131, DOI: 10.1016/j.apsusc.2016.11.19222https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFent7fJ&md5=a7633b2983d86db735de36600bee22b8The influence of tertiary butyl hydrazine as a co-reactant on the atomic layer deposition of silverGolrokhi, Zahra; Marshall, Paul A.; Romani, Simon; Rushworth, Simon; Chalker, Paul R.; Potter, Richard J.Applied Surface Science (2017), 399 (), 123-131CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)Ultra-thin conformal silver films are the focus of development for applications such as anti-microbial surfaces, optical components and electronic devices. In this study, metallic silver films have been deposited using direct liq. injection thermal at. layer deposition (ALD) using (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) as the metal source and tert-Bu hydrazine (TBH) as a co-reactant. The process provides a 23 °C wide self-limiting ALD temp. window between 105 and 128 °C, which is significantly wider than is achievable using alc. as a co-reactant. A mass deposition rate of ∼20 ng/cm2/cycle (∼0.18 Å/cycle) is obsd. under self-limiting growth conditions. The resulting films are cryst. metallic silver with a near planar film-like morphol. which are elec. conductive. By extending the temp. range of the ALD window by the use of TBH as a co-reactant, it is envisaged that the process will be exploitable in a range of new low temp. applications.
- 23Hagen, D. J.; Connolly, J.; Povey, I. M.; Rushworth, S.; Pemble, M. E. Island Coalescence during Film Growth: An Underestimated Limitation of Cu ALD. Adv. Mater. Interfaces 2017, 4, 1700274, DOI: 10.1002/admi.201700274There is no corresponding record for this reference.
- 24Li, Z.; Rahtu, A.; Gordon, R. G. Atomic Layer Deposition of Ultrathin Copper Metal Films from a Liquid Copper(I) Amidinate Precursor. J. Electrochem. Soc. 2006, 153, C787– C794, DOI: 10.1149/1.233863224https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XhtFeksb7I&md5=02e090476ba70213f186f685cf9589a9Atomic Layer Deposition of Ultrathin Copper Metal Films from a Liquid Copper(I) Amidinate PrecursorLi, Zhengwen; Rahtu, Antti; Gordon, Roy G.Journal of the Electrochemical Society (2006), 153 (11), C787-C794CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)We report a method for producing thin, completely continuous and highly conductive copper films conformally inside very narrow holes with aspect ratios over 35:1 by at. layer deposition (ALD). Pure copper thin films were grown from a novel copper(I) amidinate precursor, copper(I) N,N'-di-sec-butylacetamidinate, and mol. hydrogen gas as the reducing agent. This copper precursor is a liq. during vaporization because its m.p. (77°C) is lower than its vaporization temp. (90-120°C). Thus, the transport of the precursor vapor is very reproducible and controllable. Carbon and oxygen impurities were below 1 atom %. The growth per cycle varied from 1.5-2 A/cycle on SiO2 or Si3N4 surfaces but was only 0.1-0.5 A/cycle on metallic Ru, Cu, and Co surfaces. On oxide surfaces, copper atoms form isolated copper crystallites that merge into rough polycryst. films after more deposition cycles. On Ru and Co metal surfaces ALD Cu nucleates densely, forming smooth and strongly adherent films that are continuous even for films as thin as 4 at. layers. With 4 nm Cu deposited on 2 nm Ru substrates, the sheet resistance is below 50 Ω/.box., which is low enough for making seed layers for electroplating Cu interconnect wires.
- 25Martensson, P.; Carlsson, J. O. Atomic Layer Epitaxy of Copper Growth and Selectivity in the Cu(ll)-2,2,6,6-tetramethyl-3,5-heptanedionate/H2 Process. J. Electrochem. Soc. 1998, 145, 2926– 2931, DOI: 10.1149/1.183873825https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXltFGnsLw%253D&md5=1104c16a4d393d48fdf2569f1545c597Atomic layer epitaxy of copper growth and selectivity in the Cu(II)-2,2,6,6-tetramethyl-3,5-heptanedionate/H2 processMartensson, Per; Carlsson, Jan-OttoJournal of the Electrochemical Society (1998), 145 (8), 2926-2931CODEN: JESOAN; ISSN:0013-4651. (Electrochemical Society)The deposition of Cu by at. layer epitaxy is reported. Using Cu(II)-2,2,6,6-tetramethyl-3,5-heptanedionate as the precursor, pure and specular Cu films were deposited at deposition temps. <200°. This is >150° lower than in previous reports for the same precursor where CVD was employed. The process was self-limited in the temp. range 190 to 260°. Area-selective deposition was achieved on Pt seeded substrates vs. unseeded glass slides or oxidized metal surfaces in the temp. range 175 to 300°. At higher temps., the selectivity was lost, and nucleation was independent of substrate material because of thermal decompn. of the precursor.
- 26Wack, S.; Lunca Popa, P.; Adjeroud, N.; Guillot, J.; Pistillo, B. R.; Leturcq, R. Large-Scale Deposition and Growth Mechanism of Silver Nanoparticles by Plasma-Enhanced Atomic Layer Deposition. J. Phys. Chem. C 2019, 123, 27196– 27206, DOI: 10.1021/acs.jpcc.9b0647326https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhvVylsLzI&md5=7de0be978c5ab3bcce10537d6ac4a448Large-Scale Deposition and Growth Mechanism of Silver Nanoparticles by Plasma-Enhanced Atomic Layer DepositionWack, Sabrina; Lunca Popa, Petru; Adjeroud, Noureddine; Guillot, Jerome; Pistillo, Bianca Rita; Leturcq, RenaudJournal of Physical Chemistry C (2019), 123 (44), 27196-27206CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)The control of nanometer-scale metallic silver particles morphol. and their functional properties on a large scale represent a key factor for applications such as plasmonics, sensors, catalysts, or antimicrobial surfaces. The present work investigates in detail the growth of Ag nanoparticles deposited by plasma-enhanced at. layer deposition (PE-ALD), from triethylphosphine(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate)silver(I) [Ag(fod)(PEt3)-C16H25AgF7O2P] as the Ag precursor and H2 as the reducing agent. The uniformity of the deposition in terms of nanoparticle morphol. and chem. compn. over a large surface area (8 in.) is analyzed using an original method. For all morphol., crystallog., and chem. quantities, we report both the value at the center position and more originally, the gradient over a 10 cm distance on the substrate. The evolution of the gradient provides significant information on the growth mechanism. An effective growth rate of 0.020 ± 0.003 nm/cycle at 130 °C detd. by energy-dispersive X-ray spectroscopy is found uniformly over the whole 8-in. area of the sample. According to X-ray diffraction and X-ray photoemission spectroscopy performed on the whole silicon wafer, the deposited material is made of polycryst. pure metallic Ag, with a low amt. of impurities emanating from the precursor, showing the completeness of the redn. reaction. Under self-limiting conditions, the effects of the chamber temp. and cycle no. on the morphol. of Ag nanoparticles deposited on silicon are analyzed. The results suggests that the Ag thin films mainly evolve following a material transfer. Two potential mechanisms are in competition: the migration of the particles and their further coalescence through the Volmer-Weber growth mode or a "surface Ostwald ripening"-like process. Under certain conditions, this last mechanism could explain the nonuniformity of the deposition.
- 27Ni, C.; Shah, P.; Sarangan, A. M. Effects of different wetting layers on the growth of smooth ultra-thin silver thin films. In Proceedings of SPIE, Nanoengineering: Fabrication, Properties, Optics, and Devices XI; Campo, E. M.; Dobisz, E. A.; Eldada, L. A., Eds.; International Society for Optics and Photonics: San Diego, California, United States, August 2014 Vol. 9170.There is no corresponding record for this reference.
- 28Lazzari, R.; Jupille, J. Silver Layers on Oxide Surfaces: Morphology and Optical Properties. Surf. Sci. 2001, 482-485, 823– 828, DOI: 10.1016/S0039-6028(01)00935-928https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXltVajt7o%253D&md5=0da472be7901200f304d555b5f139b35Silver layers on oxide surfaces. Morphology and optical propertiesLazzari, R.; Jupille, J.Surface Science (2001), 482-485 (Pt. 2), 823-828CODEN: SUSCAS; ISSN:0039-6028. (Elsevier Science B.V.)Trends in the wetting of oxide substrates by Ag are tested by surface differential reflectance via the detn. of the aspect ratio of the Ag clusters: (i) the wetting of α-Al2O3(0 0 0 1) substrates by Ag, which is quite poor, is strongly improved by Ti predeposition, provided that the Ti is metallic; (in particular, the exposure of the Ag/Ti/Al2O3 system to O leads to a dewetting of the Ag layer;) (ii) On a less insulating substrate than Al2O3 (8.9 eV band gap), the ZnO(0 0 0 1)-O surface (3.3 eV band gap), Ag forms clusters with much higher aspect ratio (diam./height) than on Al2O3. However, in all cases, Ag films growth in a Volmer-Weber mode.
- 29Chen, W.; Thoreson, M. D.; Ishii, S.; Kildishev, A. V.; Shalaev, V. M. Ultra-Thin Ultra-Smooth and Low-Loss Silver Films on a Germanium Wetting Layer. Opt. Express 2010, 18, 5124– 5134, DOI: 10.1364/OE.18.00512429https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXivFOgs7o%253D&md5=69331605bc0182606cf2ea700df4a7a6Ultra-thin ultra-smooth and low-loss silver films on a germanium wetting layerChen, Weiqiang; Thoreson, Mark D.; Ishii, Satoshi; Kildishev, Alexander V.; Shalaev, Vladimir M.Optics Express (2010), 18 (5), 5124-5134CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)We demonstrate a method to fabricate ultra-thin, ultra-smooth and low-loss silver (Ag) films using a very thin germanium (Ge) layer as a wetting material and a rapid post-annealing treatment. The addn. of a Ge wetting layer greatly reduces the surface roughness of Ag films deposited on a glass substrate by electron-beam evapn. The percolation threshold of Ag films and the minimal thickness of a uniformly continuous Ag film were significantly reduced using a Ge wetting layer in the fabrication. A rapid post-annealing treatment is demonstrated to reduce the loss of the ultra-thin Ag film to the ideal values allowed by the quantum size effect in smaller grains. Using the same wetting method, we have also extended our studies to ultra-smooth silver-silica lamellar composite films with ultra-thin Ag sublayers.
- 30Stefaniuk, T.; Wróbel, P.; Trautman, P.; Szoplik, T. Ultrasmooth Metal Nanolayers for Plasmonic Applications: Surface Roughness and Specific Resistivity. Appl. Opt. 2014, 53, B237– B241, DOI: 10.1364/AO.53.00B23730https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtVSmur7J&md5=b5f5e48f0486f61812add21aea9d511fUltrasmooth metal nanolayers for plasmonic applications: surface roughness and specific resistivityStefaniuk, Tomasz; Wrobel, Piotr; Trautman, Pawel; Szoplik, TomaszApplied Optics (2014), 53 (10), B237-B241CODEN: APOPAI; ISSN:1559-128X. (Optical Society of America)The future of plasmonic devices depends on effective redn. of losses of surface plasmon-polariton waves propagating along metal-dielec. interfaces. Energy dissipation is caused by resistive heating at the skin-deep-thick outer layer of metal and scattering of surface waves on rough metal-dielec. interfaces. Fabrication of noble metal nanolayers with a smooth surface still remains a challenge. In this paper, Ag layers of 10, 30, and 50 nm thickness deposited directly on fused-silica substrates and with a 1 nm wetting layer of Ge, Ti, and Ni are examd. using an at.-force microscope and four-probe resistivity measurements. In the case of all three wetting layers, the specific resistivity of silver film decreases as the thickness increases. The smallest, equal 0.4 nm root mean squared roughness of Ag surface of 10 nm thickness is achieved for Ge interlayer; however, due to Ge segregation the specific resistivity of silver film in Ag/Ge/SiO2 structures is about twice higher than that in Ag/Ti/SiO2 and Ag/Ni/SiO2 sandwiches.
- 31Formica, N.; Ghosh, D. S.; Carrilero, A.; Chen, T. L.; Simpson, R. E.; Pruneri, V. Ultrastable and Atomically Smooth Ultrathin Silver Films Grown on a Copper Seed Layer. ACS Appl. Mater. Interfaces 2013, 5, 3048– 3053, DOI: 10.1021/am303147w31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktlyksrg%253D&md5=4edcd67260971eca7375eae4a5bd6919Ultrastable and Atomically Smooth Ultrathin Silver Films Grown on a Copper Seed LayerFormica, Nadia; Ghosh, Dhriti S.; Carrilero, Albert; Chen, Tong Lai; Simpson, Robert E.; Pruneri, ValerioACS Applied Materials & Interfaces (2013), 5 (8), 3048-3053CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)An effective method to deposit atomically smooth ultrathin silver (Ag) films by employing a 1 nm copper (Cu) seed layer is reported. The inclusion of the Cu seed layer leads to the deposition of films with extremely low surface roughness (<0.5 nm), while it also reduces the min. thickness required to obtain a continuous Ag film (percolation thickness) to 3 nm compared with 6 nm without the seed layer. Moreover, the Cu seed layer alters the growth mechanism of the Ag film by providing energetically favorable nucleation sites for the incoming Ag atoms leading to an improved surface morphol. and concomitant lower elec. sheet resistance. Optical measurements together with X-ray diffraction and elec. resistivity measurements confirmed that the Ag film undergoes a layer-by-layer growth mode resulting in a smaller grain size. The Cu seeded Ag growth method provides a feasible way to deposit ultrathin Ag films for nanoscale electronic, plasmonic, and photonic applications. In addn., as a result of the improved uniformity, the oxidn. of the Ag layer is strongly reduced to negligible values.
- 32Alvarez, R.; González, J. C.; Espinós, J. P.; González-Elipe, A. R.; Cueva, A.; Villuendas, F. Growth of Silver on ZnO And SnO2 Thin Films Intended for Low Emissivity Applications. Appl. Surf. Sci. 2013, 268, 507– 515, DOI: 10.1016/j.apsusc.2012.12.15632https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtF2gt70%253D&md5=065e7b3be2aec732e5243ddf140a76e0Growth of silver on ZnO and SnO2 thin films intended for low emissivity applicationsAlvarez, Rafael; Gonzalez, Juan C.; Espinos, Juan P.; Gonzalez-Elipe, Agustin R.; Cueva, Ana; Villuendas, FranciscoApplied Surface Science (2013), 268 (), 507-515CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)The authors have investigated the relationships existing between the optical properties and the growth mechanism, microstructure, and surface roughness of SnO2 and ZnO oxide films prepd. by magnetron sputtering under conditions resembling those utilized in industry. Thin films of these oxides with different thicknesses were characterized by at. force microscopy, glancing incidence X-ray diffraction (GIXRD), X-ray reflectometry, and spectroscopic ellipsometry. The roughness evolution of the film properties (d., surface roughness, and refraction index) as a function of their thickness has been evaluated within the concepts of the Dynamic Scaling Theory of thin film growth. Zinc oxide films were rougher than tin oxide films of similar thickness, indicating a different growing mechanism for the two materials. Silver was evapd. onto the surface of the two oxide thin films and its earlier stages of nucleation studied by background anal. of the X-ray photoemission spectra. A different nucleation mechanism was found depending on the nature of the oxide acting as substrate. The superior performance of the zinc oxide based low emissive coatings is related with a better wetting of silver on the surface of this oxide despite the comparatively lower roughness of the tin oxide layers.
- 33Zhang, C.; Kinsey, N.; Chen, L.; Ji, C.; Xu, M.; Ferrera, M.; Pan, X.; Shalaev, V. M.; Boltasseva, A.; Guo, L. J. High-Performance Doped Silver Films: Overcoming Fundamental Material Limits for Nanophotonic Applications. Adv. Mater. 2017, 29, 1605177, DOI: 10.1002/adma.201605177There is no corresponding record for this reference.
- 34Masango, S. S.; Peng, L.; Marks, L. D.; Van Duyne, R. P.; Stair, P. C. Nucleation and Growth of Silver Nanoparticles by AB and ABC-Type Atomic Layer Deposition. J. Phys. Chem. C 2014, 118, 17655– 17661, DOI: 10.1021/jp504067c34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtFChur%252FI&md5=31d8bc5461e48ec61f5d96f0b99ba8adNucleation and Growth of Silver Nanoparticles by AB and ABC-Type Atomic Layer DepositionMasango, Sicelo S.; Peng, Lingxuan; Marks, Laurence D.; Van Duyne, Richard P.; Stair, Peter C.Journal of Physical Chemistry C (2014), 118 (31), 17655-17661CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)Synthesis strategies to produce Ag nanoparticles by AB-type and ABC-type at. layer deposition (ALD) using trimethylphosphine(hexafluoroacetylacetonato) silver(I) ((hfac)Ag(PMe3)) and formalin (AB-type) and (hfac)Ag(PMe3), trimethylaluminum, and H2O (ABC-type) are reported. In situ quartz crystal microbalance measurements reveal an Ag growth rate of 1-2 ng/cm2/cycle by ABC-type ALD at 110°C and 2-10 ng/cm2/cycle for AB-type ALD at 170-200°C. AB-type Ag ALD has a nucleation period before continuous linear growth that is shorter at 200°C. Transmission electron microscopy reveals that AB-type Ag ALD particles have an av. size of ∼1.8 nm after 10 cycles. ABC-type Ag ALD particles have an av. size of ∼2.2 nm after 20 cycles. With increasing ALD cycles, ABC-type Ag ALD increases the metal loading while maintaining the particle size but AB-type Ag ALD results in the formation of bigger particles in addn. to small particles. The ability to synthesize supported metal nanoparticles with well-defined particle sizes and narrow size distributions makes ALD an attractive synthesis method compared with conventional wet chem. techniques.
- 35Dhakal, D.; Assim, K.; Lang, H.; Bruener, P.; Grehl, T.; Georgi, C.; Waechtler, T.; Ecke, R.; Schulz, S. E.; Gessner, T. Atomic Layer Deposition of Ultrathin Cu2O and Subsequent Reduction to Cu Studied by In Situ X-Ray Photoelectron Spectroscopy. J. Vac. Sci. Technol., A 2016, 34, 01A111 DOI: 10.1116/1.4933088There is no corresponding record for this reference.
- 36Goldstein, J. I.; Newbury, D. E.; Michael, J. R.; Ritchie, N. W.; Scott, J. H. J.; Joy, D. C. Scanning Electron Microscopy and X-ray Microanalysis; 3rd ed.; Springer: New-York, 2003.There is no corresponding record for this reference.
- 37Kyser, D. F.; Murata, K. Quantitative Electron Microprobe Analysis of Thin Films on Substrates. IBM J. Res. Dev. 1974, 18, 352– 363, DOI: 10.1147/rd.184.035237https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE2cXltFCitbY%253D&md5=8edc8a6b9e2e4673674401b416f409faQuantitative electron microprobe analysis of thin films on substratesKyser, D. F.; Murata, K.IBM Journal of Research and Development (1974), 18 (4), 352-63CODEN: IBMJAE; ISSN:0018-8646.A Monte Carlo simulation procedure was developed for kV electron beam scattering and energy loss in target consisting of thin films on thick substrates; the calcns. have direct application to the nondestructive quant. anal. of ultra thin films with an electron microprobe. Angular elastic scattering is calcd. in the electron trajectory simulation with the screened Rutherford expression for cross section, and energy loss between elastic scattering events is calcd. by using the approxn. of Bethe. The contribution to x-ray fluorescence from the film owing to backscattered electrons from the substrate is taken into account. For elemental films the simulation predicts intensity ratios for characteristic x-rays from the films, referred to stds. of thick elemental samples. No film stds. are required, and the mass thickness of any film element on any substrate can be detd. from theor. calibration curves. The model was verified by measurements on films of Si, Cu, and Au on Al2O3, and Mn-Bi and Co-Pt films with total mass thicknesses ≤100 μg/cm2 were successfully analyzed.
- 38Murata, K.; Kotera, M.; Nagami, K. Quantitative Electron Microprobe Analysis of Thin Films on Substrates with a New Monte Carlo Simulation. J. Appl. Phys. 1983, 54, 1110– 1114, DOI: 10.1063/1.33212738https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3sXhtFylsLo%253D&md5=81e9b5d5522cff045de8d0906b5d6c79Quantitative electron microprobe analysis of thin films on substrates with a new Monte Carlo simulationMurata, Kenji; Kotera, Masatoshi; Nagami, KoichiJournal of Applied Physics (1983), 54 (2), 1110-14CODEN: JAPIAU; ISSN:0021-8979.A new Monte Carlo simulation was applied to the electron microprobe anal. of thin films at energies 1-10 keV. The simulation model utilizes the Mott cross section for elastic scattering and the modified Bethe equation of Rao Sahib-Wittry for energy loss, instead of the screened Rutherford cross section and the std. Bethe equation, resp. The new model was examd. in comparison with exptl. results for the most probable angle of transmitted electrons through a thin film, and also the depth distribution of x-ray prodn. The simulation was applied to thickness anal. of both Al and Au films on a sapphire substrate. The new results show good agreement with exptl. data. The new Monte Carlo simulation is useful for electron microprobe anal. for elements, esp. for heavy materials at relatively low energies.
- 39Murata, K.; Sugiyama, K. Quantitative Electron Microprobe Analysis of Ultrathin Gold Films on Substrates. J. Appl. Phys. 1989, 66, 4456– 4461, DOI: 10.1063/1.34394239https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3cXhsVyitg%253D%253D&md5=c4cf7e66d7a9a371e0c6d81086df82beQuantitative electron microprobe analysis of ultrathin gold films on substratesMurata, Kenji; Sugiyama, KatsuyaJournal of Applied Physics (1989), 66 (9), 4456-61CODEN: JAPIAU; ISSN:0021-8979.The thickness of gold thin films of 0.1-100 nm on Si substrates has been measured with an electron probe microanalyzer. The measured thickness results agree very well with exptl. ones, which are obtained with a quartz balance app. The thickness detection limit of the present method can reach submonolayer films.
- 40Campos, C. S.; Vasconcellos, M. A. Z.; Llovet, X.; Salvat, F. Thickness Determination of Ultra-Thin Films on Si Substrates by EPMA. Microchim. Acta 2004, 145, 13– 17, DOI: 10.1007/s00604-003-0120-340https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjsVWjsb8%253D&md5=aeb4c4fc6473bec9f5c41f4a9302094dThickness determination of ultrathin films on silicon substrates by EPMACampos, Christiani S.; Vasconcellos, Marcos A. Z.; Llovet, Xavier; Salvat, FrancescMicrochimica Acta (2004), 145 (1-4), 13-17CODEN: MIACAQ; ISSN:0026-3672. (Springer-Verlag Wien)Results from thickness detn. of single-element ultrathin (<10 nm) films by electron probe microanal. (EPMA) are presented. The studied samples were Ge, Sn, Ag, and Au thin films deposited by resistive evapn. on Si substrates. The thickness of the films was controlled during evapn. by means of a quartz crystal, previously calibrated using samples with overlayers of different thicknesses (>20 nm) measured by Rutherford backscatter spectrometry and optical interferometry. EPMA measurements were performed on an electron microprobe CAMECA SX-50, with incident electron energies ranging from 4 keV to 20 keV. Film thicknesses were derived from the measured k-ratios using the anal. programs X-Film and Layerf and the Monte Carlo simulation code Penelope. The ionization cross sections used in the simulations were calcd. with the distorted-wave Born approxn. Film thicknesses obtained from the EPMA measurements using the various computational methods are compared with those measured with the quartz crystal. The max. relative difference between results from the different techniques does not exceed 5%.
- 41Drouin, D.; Couture, A. R.; Joly, D.; Tastet, X.; Aimez, V.; Gauvin, R. CASINO V2.42–A Fast and Easy-to-use Modeling Tool for Scanning Electron Microscopy and Microanalysis Users. Scanning 2007, 29, 92– 101, DOI: 10.1002/sca.2000041https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnvVensL4%253D&md5=40f92d9c001f910844da3e298d18fb42CASINO V2.42-a fast and easy-to-use modeling tool for scanning electron microscopy and microanalysis usersDrouin, Dominique; Couture, Alexandre Real; Joly, Dany; Tastet, Xavier; Aimez, Vincent; Gauvin, RaynaldScanning (2007), 29 (3), 92-101CODEN: SCNNDF; ISSN:0161-0457. (John Wiley & Sons Ltd.)Monte Carlo simulations have been widely used by microscopists for the last few decades. In the beginning it was a tedious and slow process, requiring a high level of computer skills from users and long computational times. Recent progress in the microelectronics industry now provides researchers with affordable desktop computers with clock rates greater than 3 GHz. With this type of computing power routinely available, Monte Carlo simulation is no longer an exclusive or long (overnight) process. The aim of this paper is to present a new user-friendly simulation program based on the earlier CASINO Monte Carlo program. The intent of this software is to assist scanning electron microscope users in interpretation of imaging and microanal. and also with more advanced procedures including electron-beam lithog. This version uses a new architecture that provides results twice as quickly. This program is freely available to the scientific community and can be downloaded from the website: www.gel.usherb.ca/casino.
- 42Drouin, D.; Hovington, P.; Gauvin, R. CASINO: A New Monte Carlo Code in C Language for Electron Beam Interactions–Part II: Tabulated Values of the Mott Cross Section. Scanning 1997, 19, 20– 28, DOI: 10.1002/sca.495019010342https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmvFynsro%253D&md5=24d300f3ab7a4f9f4a0df5ac87ecba69CASINO: a new Monte Carlo code in C language for electron beam interactions - part II: Tabulated values of the Mott cross sectionDrouin, Dominique; Hovington, Pierre; Gauvin, RaynaldScanning (1997), 19 (1), 20-28CODEN: SCNNDF; ISSN:0161-0457. (FAMS, Inc.)This paper presents routines to compute the Mott cross section used in the CASINO program (Monte CArlo SImulation of electroN trajectory in sOlid). The routines used tabulated values of the Mott cross section computed in the work of Czyzewski et al. (1990). The cross section is available over the range 0.02 to 30 keV and for the first 94 elements of the Periodic Table. The routines are written in C language and use a binary file to interpolate the cross section. The first routine computes the total Mott cross sections; the second calcs. the polar angle of collision. Backscattered coeffs. computed using different cross section are compared for C, Al, Ag, and Au. The Rutherford (1911) cross section and the available empirical equations (Browning et al. 1994, Gauvin and Drouin 1993) are compared to tabulated values of Mott. Also, the energy distribution of backscattered electrons is shown for Al and Au at 10 keV. Finally, the relative computation times for the different Mott cross sections are compared. It was found that tabulated Mott cross sections are more accurate and faster than any empirical Mott cross sections. The tabulated Mott cross sections are even faster than simple Rutherford cross sections.
- 43Hovington, P.; Drouin, D.; Gauvin, R. CASINO: A New Monte Carlo Code in C Language for Electron Beam Interaction–Part I: Description of the Program. Scanning 1997, 19, 1– 14, DOI: 10.1002/sca.495019010143https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmvFynsr0%253D&md5=a445397baf9fd4af8694601b5cb66178CASINO: a new Monte Carlo code in C language for electron beam interaction - part I: Description of the programHovington, Pierre; Drouin, Dominique; Gauvin, RaynaldScanning (1997), 19 (1), 1-14CODEN: SCNNDF; ISSN:0161-0457. (FAMS, Inc.)This paper is a guide to the ANSI std. C code of CASINO program which is a single scattering Monte CArlo SImulation of electroN trajectory in sOlid specially designed for low-beam interaction in a bulk and thin foil. CASINO can be used either on a DOS-based PC or on a UNIX-based workstation. This program uses tabulated Mott elastic cross sections and exptl. detd. stopping powers. Function pointers are used for the most essential routine so that different phys. models can easily be implemented. CASINO can be used to generate all of the recorded signals (x-rays, secondary, and backscattered) in a scanning electron microscope either as a point anal., as a linescan, or as an image format, for all the accelerated voltages (0.1-30 kV). As an example of application, it was found that a 20 nm Guinier-Preston Mg2Si in a light aluminum matrix can, theor., be imaged with a microchannel backscattered detector at 5 keV with a beam spot size of 5 nm.
- 44Arts, K.; Vandalon, V.; Puurunen, R. L.; Utriainen, M.; Gao, F.; Kessels, W. M. M.; Knoops, H. C. M. Sticking Probabilities of H2O and Al(CH3)3 During Atomic Layer Deposition of Al2O3 Extracted from their Impact on Film Conformality. J. Vac. Sci. Technol., A 2019, 37, 030908 DOI: 10.1116/1.509362044https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXosVOns74%253D&md5=9b0d5be3ba07ae8b06cdec6c59b2de73Sticking probabilities of H2O and Al(CH3)3 during atomic layer deposition of Al2O3 extracted from their impact on film conformalityArts, Karsten; Vandalon, Vincent; Puurunen, Riikka L.; Utriainen, Mikko; Gao, Feng; Kessels, Wilhelmus M. M.; Knoops, Harm C. M.Journal of Vacuum Science & Technology, A: Vacuum, Surfaces, and Films (2019), 37 (3), 030908/1-030908/5CODEN: JVTAD6; ISSN:0734-2101. (American Institute of Physics)The conformality of a film grown by at. layer deposition (ALD) is strongly affected by the reactivities of the precursor and coreactant, which can be expressed in terms of their sticking probabilities toward the surface. We show that the leading front of the thickness profile in high-aspect-ratio structures gives direct information on the sticking probabilities of the reactants under most conditions. The slope of the front has been used to det. the sticking probabilities of Al(CH3)3 and H2O during ALD of Al2O3. The detd. values are (0.5-2) × 10-3 for Al(CH3)3 and (0.8-2) × 10-4 for H2O at a set-point temp. of 275°C, corresponding to an estd. substrate temp. of 220°C. Addnl., the thickness profiles reveal soft-satn. behavior during the H2O step, most dominantly at reduced temps., which can limit the conformality of Al2O3 grown by ALD. This work thus provides insights regarding quant. information on sticking probabilities and conformality during ALD, which is valuable for gaining a deeper understanding of ALD kinetics. (c) 2019 American Institute of Physics.
- 45Gao, F.; Arpiainen, S.; Puurunen, R. Microscopic Silicon-Based Lateral High-Aspect-Ratio Structures for Thin Film Conformality Analysolis. J. Vac. Sci. Technol., A 2015, 33, 010601 DOI: 10.1116/1.490394145https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitFOjsL%252FL&md5=0a4a6c187a220ba60158e005986d29abMicroscopic silicon-based lateral high-aspect-ratio structures for thin film conformality analysisGao, Feng; Arpiainen, Sanna; Puurunen, Riikka L.Journal of Vacuum Science & Technology, A: Vacuum, Surfaces, and Films (2015), 33 (1), 010601/1-010601/5CODEN: JVTAD6; ISSN:0734-2101. (American Institute of Physics)Film conformality is one of the major drivers for the interest in at. layer deposition (ALD) processes. This work presents new silicon-based microscopic lateral high-aspect-ratio (LHAR) test structures for the anal. of the conformality of thin films deposited by ALD and by other chem. vapor deposition means. The microscopic LHAR structures consist of a lateral cavity inside silicon with a roof supported by pillars. The cavity length (e.g., 20-5000 μm) and cavity height (e.g., 200-1000 nm) can be varied, giving aspect ratios of, e.g., 20:1 to 25 000:1. Film conformality can be analyzed with the microscopic LHAR by several means, as demonstrated for the ALD Al2O3 and TiO2 processes from Me3Al/H2O and TiCl4/H2O. The microscopic LHAR test structures introduced in this work expose a new parameter space for thin film conformality investigations expected to prove useful in the development, tuning and modeling of ALD and other chem. vapor deposition processes. (c) 2015 American Institute of Physics.
- 46Prokes, S. M.; Glembocki, O. J.; Cleveland, E.; Caldwell, J. D.; Foos, E.; Niinistö, J.; Ritala, M. Spoof-Like Plasmonic Behavior of Plasma Enhanced Atomic Layer Deposition Grown Ag Thin Films. Appl. Phys. Lett. 2012, 100, 053106 DOI: 10.1063/1.367910646https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsVaqu78%253D&md5=b04b5846473ce964e0a89c012cda82caSpoof-like plasmonic behavior of plasma enhanced atomic layer deposition grown Ag thin filmsProkes, S. M.; Glembocki, O. J.; Cleveland, Erin; Caldwell, Josh D.; Foos, Edward; Niinistoe, Jaakko; Ritala, MikkoApplied Physics Letters (2012), 100 (5), 053106/1-053106/3CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)The plasmonic behavior of Ag thin films produced by plasma enhanced at. layer deposition (PEALD) was studied. As-deposited flat PEALD Ag films exhibit unexpected plasmonic properties, and the plasmonic enhancement can differ markedly, depending on the microstructure of the Ag film. Electromagnetic field simulations indicate that this plasmonic behavior is due to air gaps that are an inherent property of the mosaic-like microstructure of the PEALD-grown Ag film, suggesting that this is a metamaterial with behavior very similar to what would be expected in spoof plasmonics where gaps are fabricated in films to create plasmonic-like resonances. (c) 2012 American Institute of Physics.
- 47Van den Bruele, F. J.; Smets, M.; Illiberi, A.; Creyghton, Y.; Buskens, P.; Roozeboom, F.; Poodt, P. Atmospheric Pressure Plasma Enhanced Spatial ALD of Silver. J. Vac. Sci. Technol., A 2015, 33, 01A131 DOI: 10.1116/1.4902561There is no corresponding record for this reference.
- 48Emslie, D. J. H.; Chadha, P.; Price, J. S. Metal ALD and Pulsed CVD: Fundamental Reactions and Links with Solution Chemistry. Coord. Chem. Rev. 2013, 257, 3282– 3296, DOI: 10.1016/j.ccr.2013.07.01048https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhs1KitrjI&md5=a3900319eabfd17cf77cc9666a09c75fMetal ALD and pulsed CVD: Fundamental reactions and links with solution chemistryEmslie, David J. H.; Chadha, Preeti; Price, Jeffrey S.Coordination Chemistry Reviews (2013), 257 (23-24), 3282-3296CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)A review. At. layer deposition (ALD) is a thin film deposition technique which operates via repeated alternating and self-terminating surface-based reactions between a precursor and a co-reactant, sepd. in time by purge steps. This technique is particularly well-suited to the deposition of highly uniform and conformal thin films, even on surfaces with nano-scale high aspect ratio features. Furthermore, use of a metal precursor and a co-reactant in ALD and the related technique of pulsed-CVD (pulsed-chem. vapor deposition), provides the potential for deposition of materials that may be inaccessible using CVD methods that rely upon the thermal decompn. of a single metal precursor. This review surveys the different classes of co-reactant used for thermal metal ALD/pulsed-CVD with a focus on the reaction chemistries known or proposed to be involved. Parallels are drawn between surface-based metal ALD/pulsed-CVD reactivity and soln.-based reactivity including electroless deposition, soln.-based nanoparticle prepn., and the prepn. of zero-valent complexes bearing labile ligands. Also described are applications of soln. screening and soln. mechanistic studies to the identification of promising new ALD/pulsed-CVD reactivities, and the generation of initial mechanistic hypotheses as to the fundamental reaction steps involved in metal ALD/pulsed-CVD. A primary goal of this review is to provide a unique reactivity-based perspective of metal ALD/pulsed-CVD. In addn., endeavored to illustrate commonalities between soln.-based and surface-based reactions relevant to metal deposition, and to highlight beneficial applications of the former to the development of the latter.
- 49Vidjayacoumar, B.; Emslie, D. J. H.; Clendenning, S. B.; Blackwell, J. M.; Britten, J. F.; Rheingold, A. Investigation of AlMe3, BEt3, and ZnEt2 as Co-Reagents for Low-Temperature Copper Metal ALD/Pulsed-CVD. Chem. Mater. 2010, 22, 4844– 4853, DOI: 10.1021/cm101442e49https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXpvFSmtbs%253D&md5=02106bc3663edb01731b20e93eec7fd1Investigation of AlMe3, BEt3, and ZnEt2 as Co-Reagents for Low-Temperature Copper Metal ALD/Pulsed-CVDVidjayacoumar, Balamurugan; Emslie, David J. H.; Clendenning, Scott B.; Blackwell, James M.; Britten, James F.; Rheingold, ArnoldChemistry of Materials (2010), 22 (17), 4844-4853CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)The reactions of AlMe3, BEt3, and ZnEt2 with toluene solns. of the copper(II) complexes [CuL2] {L = acetylacetonate (acac; 1), hexafluoroacetylacetonate (hfac; 2), N-isopropyl-β-ketiminate (acnac; 3), N,N-dimethyl-β-diketiminate (nacnac; 4), 2-pyrrolylaldehyde (PyrAld; 5), N-isopropyl-2-pyrrolylaldiminate (PyrImiPr; 6a), N-ethyl-2-pyrrolylaldiminate (PyrImEt; 6b), and N-isopropyl-2-salicylaldiminate (IPSA; 7)} were investigated, and most combinations were found to deposit metal films or metal powder at 50 °C or less. SEM and XPS of metal films deposited on ruthenium showed a range of morphologies and compns., including pure copper (excluding oxygen content after atm. exposure). These nonaq. soln. screening studies provided a rapid and convenient means to identify the most promising [CuIIL2] precursor/ERn co-reagent combinations for copper metal ALD/pulsed-CVD studies, and subsequent ALD/pulsed-CVD studies were performed using 6b in combination with AlMe3, BEt3 and ZnEt2. As in soln., the reactivity of these reagents (pulsed-CVD) followed the order ZnEt2 ≈ AlMe3 » BEt3. Furthermore, at 120-150 °C, ZnEt2 was used successfully to deposit smooth, conductive films composed of copper with 8-15% Zn. On the basis of CVD studies with ZnEt2, zinc content appears to derive from a parasitic CVD process, which becomes more favorable above 120 °C, detracting from the goal of self-limiting deposition.
- 50Raut, N. C.; Al-Shamery, K. Inkjet Printing Metals on Flexible Materials for Plastic and Paper Electronics. J. Mater. Chem. C 2018, 6, 1618– 1641, DOI: 10.1039/C7TC04804A50https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXksFOqtw%253D%253D&md5=46a12e26247c875fa52714f2a44edc3eInkjet printing metals on flexible materials for plastic and paper electronicsRaut, N. C.; Al-Shamery, K.Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2018), 6 (7), 1618-1641CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)Inorg. printed electronics is now recognized as an area of tremendous com., potential and tech. progress. Many research groups are actively involved worldwide in developing metal nanoparticle inks and precursors for printing inorg./org. materials using different printing techniques. This review article focuses on inkjet printed metal structures and their applications. It comprises ink formulation, optimal droplet formation as well as adhesion of the printed patterns at the underlying substrate and post-treatment like sintering to be considered in the initial ink design. Besides some examples demonstrating aspects on ink formulation via patterning solid surfaces such as glass and silicon oxide, special emphasis will be placed on compatibility for usage in plastic and paper electronics. Printing of nanoparticles of copper, silver, gold etc. will be discussed and will be compared to printing of a variety of metal-org. precursor inks. Finally, a brief account on exemplary applications using the printed inorg. nanoparticles/materials is provided.
- 51Mo, L.; Guo, Z.; Yang, L.; Zhang, Q.; Fang, Y.; Xin, Z.; Chen, Z.; Hu, K.; Han, L.; Li, L. Silver Nanoparticles Based Ink with Moderate Sintering in Flexible and Printed Electronics. Int. J. Mol. Sci. 2019, 20, 2124, DOI: 10.3390/ijms2009212451https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhtFKis7Y%253D&md5=032edfe9c3486926af3fa4d632f8b4faSilver nanoparticles based ink with moderate sintering in flexible and printed electronicsMo, Lixin; Guo, Zhenxin; Yang, Li; Zhang, Qingqing; Fang, Yi; Xin, Zhiqing; Chen, Zheng; Hu, Kun; Han, Lu; Li, LuhaiInternational Journal of Molecular Sciences (2019), 20 (9), 2124CODEN: IJMCFK; ISSN:1422-0067. (MDPI AG)A review. Printed electronics on flexible substrates has attracted tremendous research interest research thanks its low cost, large area prodn. capability and environmentally friendly advantages. Optimal characteristics of silver nanoparticles (Ag NPs) based inks are crucial for ink rheol., printing, post-print treatment, and performance of the printed electronics devices. In this review, the methods and mechanisms for obtaining Ag NPs based inks that are highly conductive under moderate sintering conditions are summarized. These characteristics are particularly important when printed on temp. sensitive substrates that cannot withstand sintering of high temp. Strategies to tailor the protective agents capping on the surface of Ag NPs, in order to optimize the sizes and shapes of Ag NPs as well as to modify the substrate surface, are presented. Different (emerging) sintering technologies are also discussed, including photonic sintering, elec. sintering, plasma sintering, microwave sintering, etc. Finally, applications of the Ag NPs based ink in transparent conductive film (TCF), thin film transistor (TFT), biosensor, radio frequency identification (RFID) antenna, stretchable electronics and their perspectives on flexible and printed electronics are presented.
- 52Lienhart, R. FR Patent. 015113, 2015.There is no corresponding record for this reference.
- 53Gaarenstroom, S. W.; Winograd, N. Initial and Final State Effects in the ESCA Spectra of Cadmium and Silver Oxides. J. Chem. Phys. 1977, 67, 3500– 3506, DOI: 10.1063/1.43534753https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE1cXotFGhtw%253D%253D&md5=457dc2e5101c0285a000550e2ca71b69Initial and final state effects in the ESCA spectra of cadmium and silver oxidesGaarenstroom, S. W.; Winograd, N.Journal of Chemical Physics (1977), 67 (8), 3500-6CODEN: JCPSA6; ISSN:0021-9606.The factors which influence chem. shifts are examd. in order to elucidate the cause of the anomalous chem. shifts for Cd and Ag oxides. The effects of extra-at. relaxation are accounted for using a procedure employing exptl. Auger and binding energies. At. partial ionic charges for some simple Cd, Ag, and Zn compds. are calcd. from exptl. binding energies using a model which includes the effects of lattice potentials and extra-at. relaxation. Inclusion of extra-at. relaxation effects did not have a drastic effect on the relative ionicities computed for these selected compds. However, for CdO, a large extra-at. relaxation energy contribution reduces the binding energy by 0.5 eV more than is predicted from nearest electroneg. arguments.
- 54Moulder, J. F.; Stickle, W. F.; Sobol, P. E.; Bomben, K. D. Physical Electronics Division. Handbook of X-ray Photoelectron Spectroscopy; Chastain, J., Ed.; Perkin-Elmer Corporation: Eden Prairie, Minnesota, United States, 1995.There is no corresponding record for this reference.
- 55Birkholz, M.; Fewster, P. F.; Genzel, C. Thin Film Analysis by X-ray Scattering; Wiley-VCH : Weinheim, 2006.There is no corresponding record for this reference.
- 56de Keijser, T. H.; Langford, J. I.; Mittemeijer, E. J.; Vogels, A. B. P. Use of the Voigt Function in a Single-Line Method for the Analysis of X-ray Diffraction Line Broadening. J. Appl. Crystallogr. 1982, 15, 308– 314, DOI: 10.1107/S002188988201203556https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL38XitVyrsrs%253D&md5=2600c53296f378634db7abe47d338338Use of the Voigt function in a single-line method for the analysis of x-ray diffraction line broadeningDe Keijser, T. H.; Langford, J. I.; Mittemeijer, E. J.; Vogels, A. B. P.Journal of Applied Crystallography (1982), 15 (3), 308-14CODEN: JACGAR; ISSN:0021-8898.The use of the Voigt function for the anal. of the integral breadths of broadened x-ray diffraction line profiles forms the basis of a rapid and powerful single-line method of crystallite-size and strain detn. which is easy to apply. To avoid graphical methods or interpolation from tables, empirical formulae of high accuracy are used and an estn. of errors is presented, including the influence of line-profile asymmetry. The method applied to four practical cases of size-strain broadening: (1) cold-worked Ni, (2) a nitrided steel, (3) an electrodeposited Ni layer, and (4) a liq.-quenched A-Si alloy.
- 57Johnson, P. B.; Christy, R. W. Optical Constants of the Noble Metals. Phys. Rev. B 1972, 6, 4370– 4379, DOI: 10.1103/PhysRevB.6.437057https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3sXjsFKksA%253D%253D&md5=d960c3d9476f6cabad9562e5ea3a9d6cOptical constants of the noble metalsJohnson, P. B.; Christy, R. W.Physical Review B: Solid State (1972), 6 (12), 4370-9CODEN: PLRBAQ; ISSN:0556-2805.The optical consts. n and k were obtained for Cu, Ag, and Au from reflection and transmission measurements on vacuum-evapd. thin films at room temp., in the spectral range 0.5-6.5 eV. The film-thickness range was 185-500 Å. Three optical measurements were inverted to obtain the film thickness d as well as n and k. The estd. error in d was ±2 Å, and that in n, k was <0.02 over most of the spectral range. The results in the film-thickness range 250-500 Å were independent of thickness, and were unchanged after vacuum annealing or aging in air. The free-electron optical effective masses and relaxation times derived from the results in the near ir agreed satisfactorily with previous values. The interband contribution to the imaginary part of the dielec. const. was obtained by subtracting the free-electron contribution. Some recent theor. calcns. were compared with the results for Cu and Au. In addn., some other recent expts. are crit. compared with the present results.
- 58Amendola, V.; Bakr, O. M.; Stellacci, F. A Study of the Surface Plasmon Resonance of Silver Nanoparticles by the Discrete Dipole Approximation Method: Effect of Shape, Size, Structure, and Assembly. Plasmonics 2010, 5, 85– 97, DOI: 10.1007/s11468-009-9120-458https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXjtlGnt7s%253D&md5=65ece8c3f63e53ac871ed0fff4ab399cA Study of the Surface Plasmon Resonance of Silver Nanoparticles by the Discrete Dipole Approximation Method: Effect of Shape, Size, Structure, and AssemblyAmendola, Vincenzo; Bakr, Osman M.; Stellacci, FrancescoPlasmonics (2010), 5 (1), 85-97CODEN: PLASCS; ISSN:1557-1955. (Springer)The surface plasmon resonance (SPR) of silver nanoparticles (AgNPs) was studied with the discrete dipole approxn. considering different shapes, sizes, dielec. environments, and supra-particles assemblies. In particular, we focused our simulations on AgNPs with sizes below 10 nm, where the correction of silver dielec. const. for intrinsic size effects is necessary. We found that AgNPs shape and assembly can induce distinctive features in the extinction spectra and that SPR is more intense when AgNPs have discoid or flat shapes and are embedded in a dielec. shell with high refractive index. However, the SPR loses much of its distinctive features when size effects and stabilizing mols. induce significant broadening of the extinction bands that is often obsd. in the case of thiolated AgNPs smaller than about 5 nm. These results are useful indications for in situ characterization and monitoring of AgNPs synthesis and for the engineering of AgNPs with new plasmonic properties.
- 59Drachev, V. P.; Perminov, S. V.; Rautian, S. G.; Safonov, V. P. Nonlinear Optical Effects and Selective Photomodification of Colloidal Silver Aggregates. Top. Appl. Phys. 2002, 82, 115, DOI: 10.1007/3-540-44948-5_6There is no corresponding record for this reference.
- 60Kato, K.; Omoto, H.; Tomioka, T.; Takamatsu, A. Visible and Near Infrared Light Absorbance of Ag Thin Films Deposited On ZnO Under Layers by Magnetron Sputtering. Sol. Energy Mater. Sol. Cells 2011, 95, 2352– 2356, DOI: 10.1016/j.solmat.2011.04.00560https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXntlWrtLw%253D&md5=885f0e812fce1d2a3b69c0699abf23baVisible and near infrared light absorbance of Ag thin films deposited on ZnO under layers by magnetron sputteringKato, Kazuhiro; Omoto, Hideo; Tomioka, Takao; Takamatsu, AtsushiSolar Energy Materials & Solar Cells (2011), 95 (8), 2352-2356CODEN: SEMCEQ; ISSN:0927-0248. (Elsevier B.V.)The correlation among the elec., optical and structural properties of Ag thin films was investigated. Low-emissivity (low-e) coatings consisting of glass/ZnO/Ag were deposited by magnetron sputtering. The ZnO thin films were deposited under various oxygen gas pressures to vary the property of Ag thin films deposited on them. When the ZnO thin films were deposited in low oxygen gas pressure, the Ag thin films deposited on the ZnO thin films exhibited low resistivity and smooth surface. Besides, it was found that the low-emissivity coatings with low visible and near IR light absorbance were obtained using the low-resistive and smooth Ag thin films. It was concluded from the results that the light absorbance became low with decreasing the resistivity of Ag thin films in accordance with Drude's theory in the case where the Ag thin films exhibited sufficiently smooth surface. Furthermore, it can be considered that the surface plasmon polariton of Ag thin films had an influence on the optical property when their surface became rough. The optical absorbance of the low-e coatings should be detd. as the result of the competition between two factors: resistivity and surface roughness of Ag thin films.
- 61Granqvist, C. G. Transparent Conductors as Solar Energy Materials: A Panoramic Review. Sol. Energy Mater. Sol. Cells 2007, 91, 1529– 1598, DOI: 10.1016/j.solmat.2007.04.03161https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXpt1ylu78%253D&md5=93b43c5af274d397b06367f0e27e0b17Transparent conductors as solar energy materials: A panoramic reviewGranqvist, Claes G.Solar Energy Materials & Solar Cells (2007), 91 (17), 1529-1598CODEN: SEMCEQ; ISSN:0927-0248. (Elsevier B.V.)A review. Transparent conductors (TCs) have a multitude of applications for solar energy utilization and for energy savings, esp. in buildings. The largest of these applications, in terms of area, make use of the fact that the TCs have low IR emittance and hence can be used to improve the thermal properties of modern fenestration. Depending on whether the TCs are reflecting or not in the near IR pertinent to solar irradn., the TCs can serve in "solar control" or "low-emittance" windows. Other applications rely on the elec. cond. of the TCs, which make them useful as current collectors in solar cells and for inserting and extg. elec. charge in electrochromic "smart windows" capable of combining energy efficiency and indoor comfort in buildings. This Review takes a "panoramic" view on TCs and discusses their properties from the perspective of the radiative properties in our ambience. This approach leads naturally to considerations of spectral selectivity, angular selectivity, and temporal variability of TCs, as covered in three subsequent sections. The spectrally selective materials are thin films based on metals (normally gold or titanium nitride) or wide band gap semiconductors with heavy doping (normally based on indium, tin, or zinc). Their applications to energy-efficient windows are covered in detail, exptl. as well as theor., and briefer discussions are given applications to solar cells and solar collectors. Photocatalytic properties and super-hydrophilicity are touched upon. Angular selective TCs, for which the angular properties are caused by inclined columnar nanostructures, are then covered. A discussion of TC-like materials with thermochromic and electrochromic properties follows in the final part. Detailed treatments are given for thermochromic materials based on vanadium dioxide and for electrochromic multi-layer structures (incorporating TCs as essential components). The ref. list is extensive and aims at giving an easy entrance to the many varied aspects of TCs.
- 62Butt, M. A.; Fomchenkov, S. A.; Kazanskiy, N. L.; Ullah, A.; Ali, R. Z.; Habib, M. Infrared Reflective Coatings for Building and Automobile Glass Windows for Heat Protection. In Proceedings of SPIE Optical Technologies in Telecommunications; International Society for Optics and Photonics, Samara, Russian Federation, April 2017; 2016, Vol. 10342.There is no corresponding record for this reference.
- 63Doremus, R. H. Optical Properties of Thin Metallic Films in Island Form. J. Appl. Phys. 1966, 37, 2775– 2781, DOI: 10.1063/1.1782121There is no corresponding record for this reference.
- 64Mattinen, M.; Hämäläinen, J.; Gao, F.; Jalkanen, P.; Mizohata, K.; Räisänen, J.; Puurunen, R. L.; Ritala, M.; Leskelä, M. Nucleation and Conformality of Iridium and Iridium Oxide Thin Films Grown by Atomic Layer Deposition. Langmuir 2016, 32, 10559– 10569, DOI: 10.1021/acs.langmuir.6b0300764https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFOkt7nM&md5=e1c641926c33868f722e69ad8098bf1aNucleation and Conformality of Iridium and Iridium Oxide Thin Films Grown by Atomic Layer DepositionMattinen, Miika; Hamalainen, Jani; Gao, Feng; Jalkanen, Pasi; Mizohata, Kenichiro; Raisanen, Jyrki; Puurunen, Riikka L.; Ritala, Mikko; Leskela, MarkkuLangmuir (2016), 32 (41), 10559-10569CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Nucleation and conformality are important issues, when depositing thin films for demanding applications. Iridium and iridium dioxide (IrO2) films were deposited by at. layer deposition (ALD), using five different processes. Different reactants, namely, O2, air, consecutive O2 and H2 (O2 + H2), and consecutive O3 and H2 (O3 + H2) pulses were used with iridium acetylacetonate [Ir(acac)3] to deposit Ir, while IrO2 was deposited using Ir(acac)3 and O3. Nucleation was studied using a combination of methods for film thickness and morphol. evaluation. In conformality studies, microscopic lateral high-aspect-ratio (LHAR) test structures, specifically designed for accurate and versatile conformality testing of ALD films, were used. The order of nucleation, from the fastest to the slowest, was O2 + H2 > air ≈ O2 > O3 > O3 + H2, whereas the order of conformality, from the best to the worst, was O3 + H2 > O2 + H2 > O2 > O3. In the O3 process, a change in film compn. from IrO2 to metallic Ir was seen inside the LHAR structures. Compared to the previous reports on ALD of platinum-group metals, most of the studied processes showed good to excellent results.
- 65Kim, K.; Yong, K. Highly Conformal Cu Thin-Film Growth by Low-Temperature Pulsed MOCVD. Electrochem. Solid-State Lett. 2003, 6, C106– C108, DOI: 10.1149/1.158707165https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXkvFyitLk%253D&md5=d30b60da277fa4cf62e5ab4e38a4583fHighly Conformal Cu Thin-Film Growth by Low-Temperature Pulsed MOCVDKim, Kwansoo; Yong, KijungElectrochemical and Solid-State Letters (2003), 6 (8), C106-C108CODEN: ESLEF6; ISSN:1099-0062. (Electrochemical Society)Highly conformal Cu thin films were deposited on the SiO2 trench substrate with an aspect ratio of 10 by pulsed metalorg. CVD (MOCVD) using cycles of the alternate supply of (hexafluoroacetylacetonate)Cu(I)(3,3-dimethyl-1-butene) [(hfac)Cu(DMB)] pulse and Ar purge gas. The film was 75 nm thick with a good step coverage. The growth temp. was 70° and the growth rate was 0.75-1.1 Å/cycle depending on the (hfac)Cu(DMB) pulse duration of 5-10 s. X-ray diffraction patterns of the Cu films showed a preferential crystallog. orientation of (111) plane of Cu. The impurities of C and F atom in the Cu films were below detection limits and only O atom was detected <3 av. atom% by XPS.
- 66Kikuchi, H.; Yamada, Y.; Ali, A. M.; Liang, J.; Fukushima, T.; Tanaka, T.; Koyanagi, M. Tungsten Through-Silicon via Technology for Three-Dimensional LSIs. Jpn. J. Appl. Phys. 2008, 47, 2801– 2806, DOI: 10.1143/JJAP.47.280166https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXlsl2lsrk%253D&md5=1cb9565a20a60c6f48291de88ce4d535Tungsten through-silicon via technology for three-dimensional LSIsKikuchi, Hirokazu; Yamada, Yusuke; Ali, Atif Mossad; Liang, Jun; Fukushima, Takafumi; Tanaka, Tetsu; Koyanagi, MitsumasaJapanese Journal of Applied Physics (2008), 47 (4, Pt. 2), 2801-2806CODEN: JJAPB6 ISSN:. (Japan Society of Applied Physics)Tungsten through-silicon via (W-TSV) technol. is investigated for the fabrication of three-dimensional (3D) LSI chips having low-resistive TSVs with a width less than 3 μm. In the 3D integration technol., completed two-dimensional (2D) LSI chips including metal-oxide-semiconductor field-effect transistors (MOSFETs) and metal wirings are vertically stacked through a no. of short vertical interconnections called TSV with lengths ranging from several microns to several tens of microns. The W-TSV technol. is mainly divided into three low-temp. processes: deep-trench etching, dielec. layer formation, and filling with a conductive material. We successfully formed deep Si trenches through a 6-μm-thick SiO2 dielec. layer by the modified Bosch process. The depth of the resulting Si trenches with a dielec. layer is approx. 40 μm. A SiO2 layer was formed at the bottom and on the sidewall of the Si trenches by sub-atm. chem. vapor deposition (SACVD) method using tetraethylorthosilicate (TEOS) and O3. In addn., we succeeded in uniformly depositing a conformal W metal layer by time-modulated W-CVD method at 300°.
- 67Song, M.; Wang, D.; Peana, S.; Choudhury, S.; Nyga, P.; Kudyshev, Z. A.; Yu, H.; Boltasseva, A.; Shalaev, V. M.; Kildishev, A. V. Colors with Plasmonic Nanostructures: a Full-Spectrum Review. Appl. Phys. Rev. 2019, 6, 041308 DOI: 10.1063/1.511005167https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXitVCgu7%252FE&md5=b89cc47ab4efec652a7b753476566b01Colors with plasmonic nanostructures: A full-spectrum reviewSong, Maowen; Wang, Di; Peana, Samuel; Choudhury, Sajid; Nyga, Piotr; Kudyshev, Zhaxylyk A.; Yu, Honglin; Boltasseva, Alexandra; Shalaev, Vladimir M.; Kildishev, Alexander V.Applied Physics Reviews (2019), 6 (4), 041308CODEN: APRPG5; ISSN:1931-9401. (American Institute of Physics)Since ancient times, plasmonic structural coloring has inspired humanity; glassmakers achieved vibrant colors by doping glass with metal nanoparticles to craft beautiful objects such as the Roman Lycurgus cup and stained glass. These lovely color filtering effects are a consequence of the resonant coupling of light and free electrons in metal nanoparticles, known as surface plasmons. Thanks to the continuing improvement of nanofabrication technol., the dimensions of nanoparticles and structures can now be precisely engineered to form "optical nanoantennas," allowing for control of optical response at an unprecedented level. Recently, the field of plasmonic structural coloring has seen extensive growth. In this review, we provide an up-to-date overview of various plasmonic color filtering approaches and highlight their uses in a broad palette of applications. Various surface plasmon resonance modes employed in the plasmonic color filtering effect are discussed. We first review the development of the pioneering static plasmonic colors achieved with invariant optical nanoantennas and ambient environment, then we address a variety of emerging approaches that enable dynamic color tuning, erasing, and restoring. These dynamic color filters are capable of actively changing the filtered colors and carrying more color information states than the static systems. Thus, they open an avenue to high-d. data storage, information encryption, and plasmonic information processing. Finally, we discuss the challenges and future perspectives in this exciting research area. (c) 2019 American Institute of Physics.
- 68Gudur, A.; Ji, H.-F. Bio-Applications of Nanopillars. Front. Nanosci. Nanotechnol. 2016, 2, 1– 10There is no corresponding record for this reference.
- 69Choudhury, B. D.; Casquel, R.; Bañuls, M. J.; Sanza, F. J.; Laguna, M. F.; Holgado, M.; Puchades, R.; Maquieira, A.; Barrios, C. A.; Anand, S. Silicon Nanopillar Arrays with SiO2 Overlayer for Biosensing Application. Opt. Mater. Express 2014, 4, 1345– 1354, DOI: 10.1364/OME.4.001345There is no corresponding record for this reference.
- 70Dong, H.; Hinestroza, J. P. Metal Nanoparticles on Natural Cellulose Fibers: Electrostatic Assembly and In Situ Synthesis. ACS Appl. Mater. Interfaces 2009, 1, 797– 803, DOI: 10.1021/am800225j70https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXjvVegtbs%253D&md5=c00600a9b72728c3b9f25a387474cca8Metal Nanoparticles on Natural Cellulose Fibers: Electrostatic Assembly and In Situ SynthesisDong, Hong; Hinestroza, Juan P.ACS Applied Materials & Interfaces (2009), 1 (4), 797-803CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)The conformal deposition of metal nanoparticles (Au, Pd, and Pt) onto natural cellulose fibers using two chem. strategies is reported. The driving mechanism responsible for the high surface coverage of the substrates was identified as the electrostatic interactions between the pos. charged cellulose and the either neg. charged nanoparticles or neg. metal complex ions. The natural cellulose fibers were rendered cationic by grafting ammonium ions, using an epoxy substitution reaction, to the abundant hydroxyl groups present in cellulose mols. The first method involved the electrostatic assembly of citrate-stabilized metal nanoparticles directly onto the cationic surfaces of cellulose. The second method involved the adsorption of neg. metal complex ions onto the cationic cellulose followed by a redn. reaction. The attained metal nanoparticles bound with cellulose fibers were characterized by electron microscopy (TEM and SEM) and energy-dispersive X-ray spectroscopy (EDX). Both pathways generated metal nanoparticles with high packing densities on the cellulose substrates even when very dil. solns. of metal colloids or metal salts were used. Achieving high surface coverage with low-concn. precursor solns. may open an avenue for the prodn. of flexible catalytic mantles or highly functionalized textile substrates.
- 71Vaish, A.; Krueger, S.; Dimitriou, M.; Majkrzak, C.; Vanderah, D. J.; Chen, L.; Gawrisch, K. Enhancing the Platinum Atomic Layer Deposition Infiltration Depth Inside Anodic Alumina Nanoporous Membrane. J. Vac. Sci. Technol., A 2015, 33, 01A148 DOI: 10.1116/1.4904398There is no corresponding record for this reference.
- 72Kariniemi, M.; Niinistö, J.; Vehkamäki, M.; Kemell, M.; Ritala, M.; Leskelä, M.; Putkonen, M. Conformality of Remote Plasma-Enhanced Atomic Layer Deposition Processes: An Experimental Study. J. Vac. Sci. Technol., A 2012, 30, 01A115 DOI: 10.1116/1.3659699There is no corresponding record for this reference.
- 73Golrokhi, Z.; Chalker, S.; Sutcliffe, C. J.; Potter, R. J. Self-Limiting Atomic Layer Deposition of Conformal Nanostructured Silver Films. Appl. Surf. Sci. 2016, 364, 789– 797, DOI: 10.1016/j.apsusc.2015.12.12773https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXitFSlt7rF&md5=2d1b5da6238d67a3302dcbea0647d41fSelf-limiting atomic layer deposition of conformal nanostructured silver filmsGolrokhi, Zahra; Chalker, Sophia; Sutcliffe, Christopher J.; Potter, Richard J.Applied Surface Science (2016), 364 (), 789-797CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)Here we develop a self-limiting at. layer deposition (ALD) process for the deposition of conformal metallic silver nanoparticle films. The films have been deposited using direct liq. injection ALD with ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) and propan-1-ol. An ALD temp. window between 123 and 128 °C is identified and within this range self-limiting growth is confirmed with a mass deposition rate of ∼17.5 ng/cm2/cycle. The effects of temp., precursor dose, co-reactant dose and cycle no. on the deposition rate and on the properties of the films have been systematically investigated. Under self-limiting conditions, films are metallic silver with a nano-textured surface topog. and nanoparticle size is dependent on the no. of ALD cycles. The ALD reaction mechanisms have been elucidated using in-situ quartz crystal microbalance (QCM) measurements, showing chemisorption of the silver precursor, followed by heterogeneous catalytic dehydrogenation of the alc. to form metallic silver and an aldehyde.
- 74Ylilammi, M.; Ylivaara, O. M. E.; Puurunen, R. L. Modeling Growth Kinetics of Thin Films Made by Atomic Layer Deposition in Lateral High-Aspect-Ratio Structures. J. Appl. Phys. 2018, 123, 205301, DOI: 10.1063/1.502817874https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXpvVOisLw%253D&md5=15aedcfe4186f70f42131442ac9f7da9Modeling growth kinetics of thin films made by atomic layer deposition in lateral high-aspect-ratio structuresYlilammi, Markku; Ylivaara, Oili M. E.; Puurunen, Riikka L.Journal of Applied Physics (Melville, NY, United States) (2018), 123 (20), 205301/1-205301/8CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The conformality of thin films grown by at. layer deposition (ALD) is studied using all-silicon test structures with long narrow lateral channels. A diffusion model, developed in this work, is used for studying the propagation of ALD growth in narrow channels. The diffusion model takes into account the gas transportation at low pressures, the dynamic Langmuir adsorption model for the film growth and the effect of channel narrowing due to film growth. The film growth is calcd. by solving the diffusion equation with surface reactions. An efficient analytic approx. soln. of the diffusion equation is developed for fitting the model to the measured thickness profile. The fitting gives the equil. const. of adsorption and the sticking coeff. This model and Gordon's plug flow model are compared. The simulations predict the exptl. measurement results quite well for Al2O3 and TiO2 ALD processes. (c) 2018 American Institute of Physics.
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