ACS Publications. Most Trusted. Most Cited. Most Read
Low-Loss and Tunable Localized Mid-Infrared Plasmons in Nanocrystals of Highly Degenerate InN
More

OR SEARCH CITATIONS

My Activity
Publications

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:Nano Lett. 2018, 18, 9, 5681-5687
  • Open Access
Letter

Low-Loss and Tunable Localized Mid-Infrared Plasmons in Nanocrystals of Highly Degenerate InN
Click to copy article linkArticle link copied!

  • Sadegh Askari*
    Sadegh Askari
    Department of Physics, Linköping University, SE-581 83 Linköping, Sweden
    Institute for Experimental and Applied Physics, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 17, 24118 Kiel, Germany
    *E-mail: [email protected]
    More by Sadegh Askari
    Orcidhttp://orcid.org/0000-0001-7267-7510
  • Davide Mariotti
    Davide Mariotti
    Nanotechnology & Integrated Bioengineering Centre (NIBEC), Ulster University, BT37 0QB, Northern Ireland, United Kingdom
    More by Davide Mariotti
    Orcidhttp://orcid.org/0000-0003-1504-4383
  • Jan Eric Stehr
    Jan Eric Stehr
    Department of Physics, Linköping University, SE-581 83 Linköping, Sweden
    More by Jan Eric Stehr
  • Jan Benedikt
    Jan Benedikt
    Institute for Experimental and Applied Physics, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 17, 24118 Kiel, Germany
    More by Jan Benedikt
    Orcidhttp://orcid.org/0000-0002-8954-1908
  • Julien Keraudy
    Julien Keraudy
    Department of Physics, Linköping University, SE-581 83 Linköping, Sweden
    More by Julien Keraudy
  • Ulf Helmersson
    Ulf Helmersson
    Department of Physics, Linköping University, SE-581 83 Linköping, Sweden
    More by Ulf Helmersson
Open PDFSupporting Information (1)

Nano Letters

Cite this: Nano Lett. 2018, 18, 9, 5681–5687
Click to copy citationCitation copied!
https://doi.org/10.1021/acs.nanolett.8b02260
Published August 23, 2018

Copyright © 2018 American Chemical Society. This publication is licensed under CC-BY.

Abstract

Click to copy section linkSection link copied!
High Resolution Image
Download MS PowerPoint Slide

Plasmonic response of free charges confined in nanostructures of plasmonic materials is a powerful means for manipulating the light-material interaction at the nanoscale and hence has influence on various relevant technologies. In particular, plasmonic materials responsive in the mid-infrared range are technologically important as the mid-infrared is home to the vibrational resonance of molecules and also thermal radiation of hot objects. However, the development of the field is practically challenged with the lack of low-loss materials supporting high quality plasmons in this range of the spectrum. Here, we demonstrate that degenerately doped InN nanocrystals (NCs) support tunable and low-loss plasmon resonance spanning the entire midwave infrared range. Modulating free-carrier concentration is achieved by engineering nitrogen-vacancy defects (InN1–x, 0.017 < x < 0.085) in highly degenerate NCs using a nonequilibrium gas-phase growth process. Despite the significant reduction in the carrier mobility relative to intrinsic InN, the mobility in degenerate InN NCs (>60 cm2/(V s)) remains considerably higher than the carrier mobility reported for other materials NCs such as doped metal oxides, chalcogenides, and noble metals. These findings demonstrate feasibility of controlled tuning of infrared plasmon resonances in a low-loss material of III–V compounds and open a gateway to further studies of these materials nanostructures for infrared plasmonic applications.

Copyright © 2018 American Chemical Society

Subjects

what are subjects

Keywords

what are keywords
Plasmonic materials active within the mid-infrared range enable enhancing light-material interaction in a technologically important spectral range that is home to the vibrational resonances of molecules and also thermal radiation of hot objects. (1−3) In mid-infrared responsive nanostructures, the oscillation of free carriers is confined to the scales around 2 orders of magnitude smaller than the light wavelength, resulting in strong and highly localized electromagnetic fields. The energy concentrated at nanoscale can be transferred into electricity (generation of “hot electrons”), coupled with the molecular vibrations, and so forth. (1−5) Localized surface plasmon resonances (LSPRs) active in the mid-infrared range are under study for applications such as targeted chemical sensing and spectroscopy, sensing low-dimensional bio-objects (e.g., biomolecules smaller than 10 nm), thermal imaging, and heat scavenging, to name a few. (1−3) Materials studied for the mid-infrared range still struggle with limitations such as restricted spectral range (graphene), (6) low mobility (doped metal oxides), (7,8) or low concentration of charge carriers (InAs, GaN, and Si). (9) There is an urgent need of finding low-loss materials with tunable plasmonic responses and a high free carrier concentration to fully unlock the potential of plasmonics in the mid-infrared range. (2,10,11,12) Compounds of group III–V semiconductors (e.g., InAs, GaN, GaP) are studied for plasmonic applications due to their small effective electron mass which results in a high electron mobility. However, high doping (carrier concentration >1020 cm–3) of these semiconductors is not easily achievable and the plasmonic resonances reported for these materials are limited to very low energies. (7) An attractive and less-studied group III–V compound is InN that has a very low effective electron mass (lowest among the nitride semiconductors) and strong propensity for n-type conductivity which makes excellent combination for an ideal plasmonic material. A wide variation of the carrier concentration from 1017 cm–3 to more than 1021 cm–3 has been reported for thin films of InN. (13) The high concentration of free electrons in InN is explained by the special characteristic of its bandgap in which the charge neutrality level is located deep in the conduction band; that is, about 1.83 eV above the valence band maximum while the conduction band minimum is 0.67 eV above the valence band maximum. (14) Defect and impurities in InN are therefore generally of the donor type. In particular, nitrogen vacancies have the lowest formation energy among the native point defects in InN and thus are considered as a possible cause of n-type conductivity especially when the growth of InN is performed using a nonequilibrium growth process. (15)
We have investigated the plasmonic response of the degenerately doped InN nanocrystals with varying degree of nitrogen deficiency. Growth of InN nanomaterials by conventional chemical methods is very challenging due to the lack of suitable precursors and the covalent nature of the bonds which complicates control over the nucleation and growth processes; (16) that is, previous reports on the synthesis of InN NCs have proven the incompatibility of solution-based methods for controlled growth of these materials. (17−20) In fact, InN is one of the least understood of the III–V semiconductors, mostly due to the difficulties associated with its preparation both in the form of thin films and as nanomaterials. (16−22) Synthesis methods based on nonthermal plasmas are compatible with growth of semiconductors with more covalent bounds. (23) Here, we employ a novel plasma-based technique that is compatible with growth of ionically bound semiconductors and allows versatile control of the chemical composition and size of the NCs.
Figure 1a shows a schematic diagram of the process (see also section S1 in the SI document). Argon gas flows through the indium hollow cathode and the plasma is maintained by applying a pulsed electric field to the cathode which leads to sputtering of the indium cathode. Nitrogen gas added to the plasma is dissociated mainly through interaction with the highly energetic electrons in the plasma. The pulsed nature of this plasma provides a saturated vapor of highly ionized sputtered material which is favorable for the rapid growth of NCs in a nonequilibrium process. (37,38) Further detail of the experiment setup and the process is presented in the SI. The growing NCs are negatively charged in the plasma due to the higher mobility of electrons (versus ions) and it results in the fast accumulation of (positively charged) ions onto the NCs. The control over nitrogen deficiency in the NCs is achieved by changing the average applied power to the cathode in the range from 15 to 40 W, which enhances indium sputtering rate and as a result the relative concentration of In to N in the NCs. The pulse frequency and length was fixed at 500 Hz and 80 μs, respectively. Figure 1b shows no significant changes in the size distribution of the NCs while varying the applied power. Energy dispersive X-ray spectroscopy (EDX) analysis was used to determine the indium/nitrogen content in the NCs collected directly on substrates. For each synthesis condition, measurements were taken on multiple locations and the values averaged (Figure 1b); the error bars in Figure 1b correspond to the standard deviation. The results show that the nitrogen is deficient in all samples (InN1–x) and the deficiency increased from x = 0.017 to x = 0.085 with increasing the average pulse power from 15 to 40 W. The measured oxygen and carbon impurities in the samples are on a constant level (∼5–6%) independent of process conditions. We believe that these impurities mainly originates from exposure to the open atmosphere and the initial contamination of the substrate. X-ray diffraction (XRD) analysis shows that all the samples have hexagonal wurtzite structure. Figure 1c shows the XRD pattern collected for a sample prepared at applied power of 20 W. All diffraction peaks can be indexed to the different planes of wurtzite InN and the XRD profiles did not change with nitrogen content for the range studied here. We should note that the utilized plasma process allows rapid growth of NCs without chemical ligands or impurities and excellent control of the chemical composition. It is likely the nonequilibrium interaction of highly energetic ions with the bare surfaces of the growing NCs that allows for the formation of native defects buried inside the NCs.

Figure 1

Figure 1. (a) Pulsed plasma process for controlled growth of nanocrystals (NCs). The generated plasma is highly ionized and lead to high growth rates by collecting ions into the negatively charged NCs. Eimp denotes the kinetic energy of ions impinging on the NC. (b) Nanocrystal diameter and corresponding nitrogen deficiency for NCs produced by varying the average plasma power; error bars for the nitrogen deficiency represents the standard error of the mean value and for the NC diameter represents the standard deviation of the distribution for the corresponding mean value. (c) Typical XRD and SEM image (inset) of wurtzite InN NCs.

High Resolution Image
Download MS PowerPoint Slide
Figure 2a shows the infrared absorbance spectra of the NCs with varied nitrogen deficiencies. It can be seen that the resonance peak position is shifted toward higher energies in samples with higher nitrogen deficiencies. The peak position is shifted from 0.27 to 0.49 eV with increasing nitrogen deficiency in the range 0.017 < x < 0.085 in InN1–x NCs (Figure 2a). The well-defined absorption peaks and corresponding shifts across the mid-infrared region of the spectrum can be explained by the high concentration of free electrons that is increasing in NCs with increasing nitrogen deficiency (Figure 2b). The electron concentration calculated from the plasmon resonance peaks in Figure 2a (see SI for details) ranges from 1.18 × 1020 cm–3 to 3.2 × 1020 cm–3 (Figure 2b). Infrared absorption has previously been observed in InN thin films (24,25) and it has been attributed to the plasmon absorption by free electrons. The optoelectronic properties of InN NCs have rarely been studied. Palomaki et al. (26) has recently reported plasmon absorption for InN NCs prepared by a colloidal synthesis technique with an LSPR peak around 3000 nm (0.41 eV). They reported limited changes in the free electron concentration from 2.51 × 1020 cm–3 to 2.89 × 1020 cm–3 induced by chemical oxidation, which clearly highlight the stabilization of the electron concentration due to the proximity of the Fermi level to the charge neutrality level. (14) Furthermore, in this case the electron concentration was not controlled by the chemical composition of the actual NCs rather by implementing a junction at the interface between core InN NC and the oxidized shell.

Figure 2

Figure 2. (a) The FTIR spectra of the InN nanocrystals for a range of nitrogen deficiencies, InN1–x, 0.017 < x < 0.085. The absorption peak is shifted to higher energies in nanocrystals with higher nitrogen deficiency. (b) Free-electron concentration, damping factor, and optically calculated free electron mobility as a function of nitrogen deficiency in InN nanocrystals.

High Resolution Image
Download MS PowerPoint Slide
The line width of the absorbance profiles in Figure 2a is proportional to the damping of free electrons due to scattering and thus can be used for determining electron mobility (see Sections S3 in the SI). The narrow line width of the absorbance profiles with full width at half-maximum (fwhm) down to 89 meV is among the narrowest linewidths reported for plasmonic NCs (see Table 1); this strongly supports the suitability and attractiveness of InN as a plasmonic material. Electron mobility calculated from the line width of the absorbance profiles is presented in Figure 2b. Electron mobility up to a value of 64.8 cm2/(V s) is obtained which is higher than the previously reported carrier mobility for any plasmonic NC including doped metal oxides, chalcogenides, and noble metals. Table 1 compares InN NCs damping factor and mobility with several other well-studied plasmonic NCs. Recent studies shows that defect engineering of doped metal oxide can lead to an electron mobility as high as 33 cm2/(V s) (in Ce doped In2O3 NCs (31)). Electron mobility for InN NCs remains considerably higher than other plasmonic NCs owing to the nonparabolic nature of InN conduction band with values of low effective electron mass. To understand the exceptional properties of InN NCs in this context, we will next discuss the effect of changing the nitrogen content on the energy band diagram of the NCs, including Fermi level and optical bandgap.
Table 1. Comparison of Plasmonic Nanocrystals Responsive in Different Range of Spectrum
nanocrystal materialresponsive rangedamping factor (meV)effective electron mass (electron mass)electron mobility (cm Ws)
InN [this work]infrared890.03–0.2565
Au (28)visible1201.1 
Cu2–xS (27)near-infrared2100.86.9
doped metal oxidesAl/ZnO (29)infrared∼2700.38∼11.0
Sn/In2O3 (30)infrared1130.3819.9
Ce/In2O3 (31)infrared77∼0.3833.0
In&F/CdO (32)near-infrared59  
The valence band spectra obtained from XPS measurements are shown in Figure 3a. The Fermi level relative to the valence band maximum is shifted from 1.43 to 1.69 eV with increasing nitrogen deficiency of NCs, that is, the Fermi level is located deeply in the conduction band (the conduction band minimum is located at 0.67 eV from the valence band edge) and it approaches charge neutrality level in NCs with higher nitrogen deficiency (Figure 3c). It has been previously observed that the Fermi level is stabilized where the free electron concentration reaches its maximum saturated value at very high concentration of defects, (14) however the Fermi level is here well below saturation so that varying the nitrogen deficiency can effectively shift the plasmon resonance peak. The high-energy shift of the Fermi level is in agreement with the widening of the optical bandgap obtained from the ultraviolet–visible absorption measurements (Figure 3b). The bandgap is determined by extrapolating the linear part of the squared absorption coefficient (see Figure S5 in SI). The bandgap is increased from 1.28 to 1.65 eV in NCs with higher nitrogen deficiency (Figure 2b). The values obtained for the bandgap from XPS (i.e., from Figure 2a) is also included in Figure 2b for an easier and direct comparison with absorption measurements. XPS measurements produced slightly higher values and this can be explained with the downward band bending due to the surface charge accumulation effect which has been previously observed in InN thin films. (14) However, we note that the difference is small and well within experimental errors or due to intrinsic differences in the measurement and fitting techniques. The blue shift of the absorption edge in degenerate semiconductors could be due to the Burstein–Moss (BM) effect. The BM shift in InN can be calculated from the dispersion relation for the conduction band obtained from a two-band k·p perturbation model presented by Kane (33)
(1)
where Eg = 0.67 eV is the bandgap of InN, k is the wave vector, m0 is the free electron mass. Ep is an energy parameter of the Kane’s model and it is taken Ep = 10. InN, as a narrow bandgap semiconductor, has a strongly nonparabolic conduction band due to the k·p interaction between valence and conduction bands. This nonparabolicity has been taken into account in the Kane model (eq 1). The Fermi level is given by eq 1 evaluated at the Fermi wave vector kF = (3π2ne)1/3. The concentration of free electrons ne in plasmonic NCs can be estimated from the correlation between the bulk plasma oscillation frequency and the plasmon resonance frequency (see Section S3 in SI and Figure 2b). Figure 3b shows the calculated bandgap energy from eq 1 for the NCs with different nitrogen deficiency. The good agreement of the predicted BM shift with the absorption measurements is further evidence that the widening of the optical bandgap is due to the high density of free electrons. Importantly, the consistency of the results for the Fermi level and the optical gap with the BM predictions certifies that the values for electron concentration calculated from the plasmon absorption peaks are accurate.

Figure 3

Figure 3. (a) XPS valence band spectra of InN nanocrystals with different nitrogen deficiency, InN1–x, 0.017 < x < 0.085. The difference between the valence band maximum and Fermi level is increased in nanocrystals with higher nitrogen deficiency. (b) The optical bandgap in InN nanocrystals as a function of nitrogen deficiency is obtained from the ultraviolet–visible absorption measurements, XPS measurements (panel a) and calculated from Kane model. (c) Modulating free-electron concentration and Fermi level in degenerate InN1–x nanocrystals. The right panel shows localized surface plasmon frequency versus free-electron concentration. The technically important infrared ranges of spectrum are shown NIR (near-infrared), MWIR (midwave infrared), and LWIR (long-wave infrared).

High Resolution Image
Download MS PowerPoint Slide
We finally discuss the possible origin of our measured electron concentrations and further corroborate the contribution from nitrogen deficiencies. In InN, the Fermi level lies far below the charge neutrality level even in degenerate InN, so that donor-type defects such as nitrogen vacancies are energetically favorable. Particularly nitrogen vacancies can play role as major defects in materials similar to InN such as GaN and AlN. (34,35) In InN, nitrogen vacancies have the lowest formation energies among all native defects. (15,36) Hydrogen impurities incorporated into the lattice during the growth process can also effectively act as electron donors in InN, however leading to much lower concentrations of free carriers (≪1020 cm–3). (36) The higher concentration of free electrons observed with increasing nitrogen deficiency in NCs is evidence of the effective presence of electrically active nitrogen vacancies. The stable charge state of the nitrogen vacancy is 3+ for Fermi level (relative to the valence band maximum) below 0.24 eV and 1+ for higher Fermi levels. The formation energy of VN+ in the bulk InN with the Fermi level being located at the conduction band minimum is 1.0 eV and its increasing with increasing the Fermi level. However, this formation energy is considerably reduced on the surface of NCs during the growth so that it can be even negative (∼−0.13 eV (15)) under In-rich growth conditions.
The high concentration of defects (donors and acceptors) observed in films of InN grown by different techniques have not been well explained by numerical calculations based on the formation energies with assuming thermodynamic equilibrium condition, that is, the formation energies are too high. A possible reason is the deviation of the growth processes from equilibrium especially when the nonequilibrium plasma processes are involved. The nonequilibrium growth of thin films with a typical growth rate of 0.1 nm/s can lead to a nitrogen surface vacancy concentration of 2.1 × 1020 cm–3 extending several tens of nanometers into the bulk. (15) The fast nonequilibrium growth of NCs in the plasmas with the presence of highly energetic and reactive species allows the formation of nitrogen vacancy defects. A typical growth rate of NCs is much higher than the growth rate of thin films owing to the accretion of positively charged ions trapped by the negatively charged NCs inside the plasma. For instance, we have previously reported growth rate of ∼500 nm/s for copper NCs (37) which is several orders of magnitude higher than the typical growth rate of films (∼0.1 nm/s). The ion concentration in pulsed plasma is significantly higher than the neutrals concentration (>80% ions (38)) and the positive ions are accelerated to the nanoparticle over a potential that allow them to gain a kinetic energy of Eimp∼2.8 eV for singly charged ions, typically higher than the formation energy of the nitrogen vacancy defect. Under the rapid nonequilibrium growth condition of the NPs, defects formed on the surface during the growth are buried inside the NC. The concentration of vacancies can be higher at the surface of NCs which can lead to higher electron concentration on the surface similar to the surface charge accumulation widely observed in thin films of InN.
At high Fermi levels, the acceptor defects become more favorable so that intense compensation occurs in highly degenerate InN. (39−41) Nitrogen vacancies in highly degenerate InN have also a tendency toward forming clusters (or complexes) of vacancies with a reduction in the absolute defect charge. (37) Density functional theory calculations show that the clusters of nitrogen vacancies with neutral charge state become favorable. (41) Furthermore, formation of positively charged complexes is expected with a lower charge state. The concentration of the nitrogen vacancy defects can be evaluated with considering more favorable vacancies with different charge states. In the calculations, charge states of qD (donors) and qA (acceptors) with the highest stability are considered (see Section S5 in the SI document). The concentration of donors for the most favorable vacancies calculated for the NCs with different nitrogen deficiencies are shown in Figure 4a. The figure also includes the upper limit obtained for the acceptor concentration.

Figure 4

Figure 4. (a) Concentration of donor and acceptor nitrogen vacancy defects in InN nanocrystals (see SI for details). (b) Calculated mobility limited by ionized defect centers in InN presented as a function of electron concentration.

High Resolution Image
Download MS PowerPoint Slide
Carrier mobility in InN is reduced with increasing free electron concentration from a few thousands cm2/(V s) at low electron concentrations (∼1017 cm–3) to a few hundred cm2/(V s) and less at high electron concentrations (>1020 cm–3) mainly due to the scattering from ionized defect centers. (39,42) The electron mobility due to the ionized defect scattering can be calculated from the known value of the defect concentrations (Section S6 in the SI file). The calculated electron mobility corresponds to these defect concentrations are presented in Figure 4b. Electron mobility where the concentration of acceptors is negligible, no-compensation, is several times higher than the values obtained from the damping factor (Figure 4b). Therefore, significant compensation with an acceptor concentration likely lower than the free electron concentration in NCs is expected.
This article introduces InN as a promising low-loss plasmonic material. Defect engineering of degenerately doped InN allows controlled modulation of the free carrier concentration to values higher than 1020 cm–3. At such a high doping levels, the optical bandgap is significantly widened, Fermi level is shifted deeply into the conduction band, and an intense plasmon absorption band appears in the infrared range of the spectrum. Carrier concentration in our NCs could be efficiently modulated by changing nitrogen vacancy defects through using a nonequilibrium plasma-based growth process. We found plasmon resonance absorption with narrow line width and tunable peaks across the mid-infrared spectral range. The very high electron mobility of these InN NCs well above carrier mobility observed in other doped semiconductors is highly attractive toward resolving the challenge of losses in plasmonic materials. This study opens a pathway for further research of doped InN and similar semiconductors (from group III–V) nanostructures as a new class of plasmonic material.

Methods

Nanocrystals (NCs) are synthesized using a custom-made setup based on high-power pulsed plasma sputtering technique. The detailed description of the process and the experimental setup is presented in the SI (Section S1). For all the samples reported here, the operating pressure was 0.8 Torr and the argon and nitrogen gas flow rates were 80 and 20 sccm, respectively. Control over stoichiometry in nitrogen deficient NPs (InN1–x, 0.017 < x < 0.085) is achieved by changing the applied power in the range from 15 to 40 W while the other operating parameters are held constant. The NCs produced in the plasma are collected downstream of the reactor directly onto the substrates for characterizations.
Mean diameter of the NCs and size distributions are determined by scanning electron microscopy (SEM) analysis. Measurements are performed with a LEO 1550 Gemini equipped with an energy dispersive X-ray spectroscopy (EDX) detector (Oxford instruments). The EDX analysis are carried out by data collected from three different spots on each sample.
The X-ray diffraction (XRD) measurements are performed using a PANalytical X́pert diffractometer mounted with a hybrid monochromator/mirror, operated at 40 kV and 40 mA with a Cu anode (Cu Kα, λ = 1.540597 Å). For typical XRD measurements, a thick layer (to avoid substrate peaks) of NCs are deposited on metal-coated silicon substrates.
UV–vis absorption measurements are performed using a Perkin–Elmer, Lambda 950 UV–VIS spectrometer; samples for UV–vis measurements are collected on glass substrates.
The Fourier transform infrared (FTIR) spectroscopy is carried out using an attenuated total reflectance (ATR) accessory. The ATR–FTIR spectrometer is a Bruker Vertex 70 FTIR spectrometer, and for the measurements, the collected sample powder on a metal coated silicon substrate is placed on the top of the ATR crystal.
X-ray photoelectron spectroscopy (XPS) measurements are performed using an Kratos Ultra photoelectron spectrometer equipped with a monochromated Al Kα (1486.6 eV) X-ray source operating at 150 W. The carbon peak C 1s at 284.3 eV was used for calibrating the spectra.

Supporting Information

Click to copy section linkSection link copied!

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.nanolett.8b02260.

  • Details of the pulsed plasma process for growth of nanocrystals, FTIR spectra of nanocrystals with different sizes, calculations of the effective electron mass, and free electron concentration, UV–visible absorption measurements, and calculations of the nitrogen vacancies and electron mobility (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

Click to copy section linkSection link copied!
  • Corresponding Author
    • Sadegh Askari - Department of Physics, Linköping University, SE-581 83 Linköping, Sweden;  Institute for Experimental and Applied Physics, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 17, 24118 Kiel, Germany;  Orcidhttp://orcid.org/0000-0001-7267-7510;  Email: [email protected]
  • Authors
    • Davide Mariotti - Nanotechnology & Integrated Bioengineering Centre (NIBEC), Ulster University, BT37 0QB, Northern Ireland, United Kingdom;  Orcidhttp://orcid.org/0000-0003-1504-4383
    • Jan Eric Stehr - Department of Physics, Linköping University, SE-581 83 Linköping, Sweden
    • Jan Benedikt - Institute for Experimental and Applied Physics, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 17, 24118 Kiel, Germany;  Orcidhttp://orcid.org/0000-0002-8954-1908
    • Julien Keraudy - Department of Physics, Linköping University, SE-581 83 Linköping, Sweden
    • Ulf Helmersson - Department of Physics, Linköping University, SE-581 83 Linköping, Sweden
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

Click to copy section linkSection link copied!

The authors would like to thank the Knut and Alice Wallenberg Foundation (Grant KAW 14.0276) and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (faculty Grant SFO-Mat-LiU #2009-00971) for financial support. D.M. acknowledges EPSRC financial support (award n. EP/M024938/1).

References

Click to copy section linkSection link copied!

This article references 42 other publications.

  1. 1
    Rodrigo, D.; Limaj, O.; Janner, D.; Etezadi, D.; García de Abajo, F. J.; Pruneri, V.; Altug, H. Science 2015, 349, 165,  DOI: 10.1126/science.aab2051
    Google Scholar
    1
    Mid-infrared plasmonic biosensing with graphene
    Rodrigo, Daniel; Limaj, Odeta; Janner, Davide; Etezadi, Dordaneh; Garcia de Abajo, F. Javier; Pruneri, Valerio; Altug, Hatice
    Science (Washington, DC, United States) (2015), 349 (6244), 165-168CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    IR spectroscopy is the technique of choice for chem. identification of biomols. through their vibrational fingerprints. However, IR light interacts poorly with nanometric-size mols. The authors exploit the unique electrooptical properties of graphene to demonstrate a high-sensitivity tunable plasmonic biosensor for chem. specific label-free detection of protein monolayers. The plasmon resonance of nanostructured graphene is dynamically tuned to selectively probe the protein at different frequencies and ext. its complex refractive index. Addnl., the extreme spatial light confinement in graphene, up to two orders of magnitude higher than in metals, produces an unprecedentedly high overlap with nanometric biomols., enabling superior sensitivity in the detection of their refractive index and vibrational fingerprints. The combination of tunable spectral selectivity and enhanced sensitivity of graphene opens exciting prospects for biosensing.
  2. 2
    Stanley, R. Nat. Photonics 2012, 6, 409,  DOI: 10.1038/nphoton.2012.161
    Google Scholar
    2
    Plasmonics in the mid-infrared
    Stanley, Ross
    Nature Photonics (2012), 6 (7), 409-411CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)
    A review. Plasmonics can be used to enhance mid-IR sources, sensors and detectors for applications such as chem. sensing, thermal imaging and heat scavenging. The challenge now is to integrate these technologies in cost-effective, compact and reliable platforms.
  3. 3
    Neubrech, F.; Huck, C.; Weber, K.; Pucci, A.; Giessen, H. Chem. Rev. 2017, 117, 5110,  DOI: 10.1021/acs.chemrev.6b00743
    Google Scholar
    3
    Surface-Enhanced Infrared Spectroscopy Using Resonant Nanoantennas
    Neubrech, Frank; Huck, Christian; Weber, Ksenia; Pucci, Annemarie; Giessen, Harald
    Chemical Reviews (Washington, DC, United States) (2017), 117 (7), 5110-5145CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    IR spectroscopy is a powerful tool widely used in research and industry for a label-free and unambiguous identification of mol. species. Inconveniently, its application to spectroscopic anal. of minute amts. of materials, for example, in sensing applications, is hampered by the low IR absorption cross-sections. Surface-enhanced IR spectroscopy using resonant metal nanoantennas, or short "resonant SEIRA", overcomes this limitation. Resonantly excited, such metal nanostructures feature collective oscillations of electrons (plasmons), providing huge electromagnetic fields on the nanometer scale. IR vibrations of mols. located in these fields are enhanced by orders of magnitude enabling a spectroscopic characterization with unprecedented sensitivity. In this Review, we introduce the concept of resonant SEIRA and discuss the underlying physics, particularly, the resonant coupling between mol. and antenna excitations as well as the spatial extent of the enhancement and its scaling with frequency. On the basis of these fundamentals, different routes to maximize the SEIRA enhancement are reviewed including the choice of nanostructures geometries, arrangements, and materials. Furthermore, first applications such as the detection of proteins, the monitoring of dynamic processes, and hyperspectral IR chem. imaging are discussed, demonstrating the sensitivity and broad applicability of resonant SEIRA.
  4. 4
    Clavero, C. Nat. Photonics 2014, 8, 95,  DOI: 10.1038/nphoton.2013.238
    Google Scholar
    4
    Plasmon-induced hot-electron generation at nanoparticle/metal-oxide interfaces for photovoltaic and photocatalytic devices
    Clavero, Cesar
    Nature Photonics (2014), 8 (2), 95-103CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)
    A review. Finding higher efficiency schemes for electron-hole sepn. is of paramount importance for realizing more efficient conversion of solar energy in photovoltaic and photocatalytic devices. Plasmonic energy conversion has been proposed as a promising alternative to conventional electron-hole sepn. in semiconductor devices. This emerging method is based on the generation of hot electrons in plasmonic nanostructures through electromagnetic decay of surface plasmons. Here, the fundamentals of hot-electron generation, injection and regeneration are reviewed, with special attention paid to recent progress towards photovoltaic devices. This new energy-conversion method potentially offers high conversion efficiencies, while keeping fabrication costs low. However, several considerations regarding the materials, architectures and fabrication methods used need to be carefully evaluated to advance this field.
  5. 5
    Tittl, A.; Michel, A. K.; Schäferling, M.; Yin, X.; Gholipour, B.; Cui, L.; Wuttig, M.; Taubner, T.; Neubrech, F.; Giessen, H. Adv. Mater. 2015, 27, 4597,  DOI: 10.1002/adma.201502023
    Google Scholar
    There is no corresponding record for this reference.
  6. 6
    Yan, H.; Low, T.; Zhu, W.; Wu, Y.; Freitag, M.; Li, X.; Guinea, F.; Avouris, P.; Xia, F. Nat. Photonics 2013, 7, 394,  DOI: 10.1038/nphoton.2013.57
    Google Scholar
    6
    Damping pathways of mid-infrared plasmons in graphene nanostructures
    Yan, Hugen; Low, Tony; Zhu, Wenjuan; Wu, Yanqing; Freitag, Marcus; Li, Xuesong; Guinea, Francisco; Avouris, Phaedon; Xia, Fengnian
    Nature Photonics (2013), 7 (5), 394-399CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)
    Plasmon is the quantum of the collective oscillation of electrons. How plasmon loses its energy (or damping) plays a pivotal role in plasmonic science and technol. Graphene plasmon is of particular interest, partly because of its potentially low damping rate. However, to date, damping pathways have not been clearly unravelled exptl. Here, we demonstrate mid-IR (4-15 μm) plasmons in graphene nanostructures with dimensions as small as 50 nm (with a mode area of ∼1 × 10-3 μm2). We also reveal damping channels via graphene intrinsic optical phonons and scattering from the edges. Plasmon lifetimes of 20 fs or less are obsd. when damping via the emission of graphene optical phonons is allowed. Furthermore, surface polar phonons in the SiO2 substrate under graphene nanostructures lead to a significantly modified plasmon dispersion and damping, in contrast to the case of a nonpolar diamond-like-carbon substrate. Our study paves the way for applications of graphene in plasmonic waveguides, modulators and detectors from sub-terahertz to mid-IR regimes.
  7. 7
    Naik, G. V.; Shalaev, V. M.; Boltasseva, A. Adv. Mater. 2013, 25, 3264,  DOI: 10.1002/adma.201205076
    Google Scholar
    7
    Alternative Plasmonic Materials: Beyond Gold and Silver
    Naik, Gururaj V.; Shalaev, Vladimir M.; Boltasseva, Alexandra
    Advanced Materials (Weinheim, Germany) (2013), 25 (24), 3264-3294CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Materials research plays a vital role in transforming breakthrough scientific ideas into next-generation technol. Similar to the way Si revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research in plasmonics and metamaterials lacks good material building blocks to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, esp. metals. There are many materials, other than conventional metallic components such as Au and Ag, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2-dimensional materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions.
  8. 8
    Mattox, T. M.; Ye, X.; Manthiram, K.; Schuck, P. J.; Alivisatos, A. P.; Urban, J. J. Adv. Mater. 2015, 27, 5830,  DOI: 10.1002/adma.201502218
    Google Scholar
    There is no corresponding record for this reference.
  9. 9
    Wagner, M.; McLeod, A. S.; Maddox, S. J.; Fei, Z.; Liu, M.; Averitt, R. D.; Fogler, M. M.; Bank, S. R.; Keilmann, F.; Basov, D. N. Nano Lett. 2014, 14, 4529,  DOI: 10.1021/nl501558t
    Google Scholar
    There is no corresponding record for this reference.
  10. 10
    Khurgin, J. b. Nat. Nanotechnol. 2015, 10, 2,  DOI: 10.1038/nnano.2014.310
    Google Scholar
    10
    How to deal with the loss in plasmonics and metamaterials
    Khurgin, Jacob B.
    Nature Nanotechnology (2015), 10 (1), 2-6CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)
    A review with commentary. Metal losses affect the performance of every plasmonic or metamaterial structure; dealing with them will det. the degree to which these structures will find practical applications.
  11. 11
    Law, S.; Podolskiy, V.; Wasserman, D. Nanophotonics 2013, 2, 103,  DOI: 10.1515/nanoph-2012-0027
    Google Scholar
    There is no corresponding record for this reference.
  12. 12
    Sachet, E.; Shelton, C. T.; Harris, J. S.; Gaddy, B. E.; Irving, D. L.; Curtarolo, S.; Donovan, B. F.; Hopkins, P. E.; Sharma, P. A.; Sharma, A. L.; Ihlefeld, J.; Franzen, S.; Maria, J.-P. Nat. Mater. 2015, 14, 414,  DOI: 10.1038/nmat4203
    Google Scholar
    12
    Dysprosium-doped cadmium oxide as a gateway material for mid-infrared plasmonics
    Sachet, Edward; Shelton, Christopher T.; Harris, Joshua S.; Gaddy, Benjamin E.; Irving, Douglas L.; Curtarolo, Stefano; Donovan, Brian F.; Hopkins, Patrick E.; Sharma, Peter A.; Sharma, Ana Lima; Ihlefeld, Jon; Franzen, Stefan; Maria, Jon-Paul
    Nature Materials (2015), 14 (4), 414-420CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    The interest in plasmonic technologies surrounds many emergent optoelectronic applications, such as plasmon lasers, transistors, sensors and information storage. Although plasmonic materials for UV-visible and near-IR wavelengths have been found, the mid-IR range remains a challenge to address: few known systems can achieve subwavelength optical confinement with low loss in this range. With a combination of expts. and ab initio modeling, here we demonstrate an extreme peak of electron mobility in Dy-doped CdO that is achieved through accurate 'defect equil. engineering'. In so doing, we create a tunable plasmon host that satisfies the criteria for mid-IR spectrum plasmonics, and overcomes the losses seen in conventional plasmonic materials. In particular, extrinsic doping pins the CdO Fermi level above the conduction band min. and it increases the formation energy of native oxygen vacancies, thus reducing their populations by several orders of magnitude. The substitutional lattice strain induced by Dy doping is sufficiently small, allowing mobility values around 500 cm2 V-1 s-1 for carrier densities above 1020 cm-3. Our work shows that CdO:Dy is a model system for intrinsic and extrinsic manipulation of defects affecting elec., optical and thermal properties, that oxide conductors are ideal candidates for plasmonic devices and that the defect engineering approach for property optimization is generally applicable to other conducting metal oxides.
  13. 13
    Wu, J. J. Appl. Phys. 2009, 106, 011101,  DOI: 10.1063/1.3155798
    Google Scholar
    13
    When group-III nitrides go infrared: New properties and perspectives
    Wu, Junqiao
    Journal of Applied Physics (2009), 106 (1), 011101/1-011101/28CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
    A review; wide-band-gap GaN and Ga-rich InGaN alloys, with energy gaps covering the blue and near-UV parts of the electromagnetic spectrum, are one group of the dominant materials for solid state lighting and lasing technologies and consequently, have been studied very well. Much less effort has been devoted to InN and In-rich InGaN alloys. A major breakthrough in 2002, stemming from much improved quality of InN films grown using mol. beam epitaxy, resulted in the bandgap of InN being revised from 1.9 eV to a much narrower value of 0.64 eV. This finding triggered a worldwide research thrust into the area of narrow-band-gap group-III nitrides. The low value of the InN bandgap provides a basis for a consistent description of the electronic structure of InGaN and InAlN alloys with all compns. It extends the fundamental bandgap of the group III-nitride alloy system over a wider spectral region, ranging from the near IR at ∼1.9 μm (0.64 eV for InN) to the UV at ∼0.36 μm (3.4 eV for GaN) or 0.2 μm (6.2 eV for AlN). The continuous range of bandgap energies now spans the near IR, raising the possibility of new applications for group-III nitrides. In this article we present a detailed review of the phys. properties of InN and related group III-nitride semiconductors. The electronic structure, carrier dynamics, optical transitions, defect physics, doping disparity, surface effects, and phonon structure will be discussed in the context of the InN bandgap re-evaluation. We will then describe the progress, perspectives, and challenges in the developments of new electronic and optoelectronic devices based on InGaN alloys. Advances in characterization and understanding of InN and InGaN nanostructures will also be reviewed in comparison to their thin film counterparts. (c) 2009 American Institute of Physics.
  14. 14
    King, P. D. C.; Veal, T. D.; Jefferson, P. H.; Hatfield, S. A.; Piper, L. F. J.; McConville, C. F.; Fuchs, F.; Furthmüller, J.; Bechstedt, F.; Lu, H.; Schaff, W. J. Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 77, 045316,  DOI: 10.1103/PhysRevB.77.045316
    Google Scholar
    There is no corresponding record for this reference.
  15. 15
    Terentjevs, A.; Catellani, A.; Cicero, G. Appl. Phys. Lett. 2010, 96, 171901,  DOI: 10.1063/1.3409224
    Google Scholar
    There is no corresponding record for this reference.
  16. 16
    Fan, G.; Wang, C.; Fang, J. Nano Today 2014, 9, 69,  DOI: 10.1016/j.nantod.2014.02.007
    Google Scholar
    16
    Solution-based synthesis of III-V quantum dots and their applications in gas sensing and bio-imaging
    Fan, Guangyin; Wang, Chenyu; Fang, Jiye
    Nano Today (2014), 9 (1), 69-84CODEN: NTAOCG; ISSN:1748-0132. (Elsevier Ltd.)
    A review. In recent years, the syntheses of III-V quantum dots have attracted extensive interests because of their remarkable quantum-confinement-effects, other attractive properties such as large exciton radius and potential applications in a no. of areas such as gas sensing and biol. probing. Some III-V members are low toxic and suitable to be used in bio-system with their excellent fluorescent characteristics. Although a soln.-phase prepn. of III-V quantum dots has become possible, the synthesis approach is still in its infancy and the quality of III-V products is inferior to those of II-VI and IV-VI quantum dots due to some difficulties such as lack of suitable precursors, high covalent characteristic, and difficult control of their nucleation and growth. The size, size distribution and crystallinity are strongly dependent on a specific reaction procedure and prepn. technique. It is also believed that the selection of suitable precursors and designing corresponding key reactions should hold the keys for a successful prodn. of the desired III-V quantum dots. This article focuses on the soln.-phase synthesis of In- and Ga-based III-V quantum dots, and these developments are presented through a classification of their chem. routes including metathesis, thermolysis, dehalosilylation and transmetalation with a discussion on their prepn. techniques such as one-pot heating-up and hot-injection. Furthermore, III-V quantum dots acted in gas sensing and bio-imaging applications are outlined as well. Eventually, an outlook of current challenges and promising direction for the development of III-V quantum dot synthesis is provided.
  17. 17
    Karan, N. S.; Chen, Y.; Liu, Z.; Beaulac, R. Chem. Mater. 2016, 28, 5601,  DOI: 10.1021/acs.chemmater.6b02417
    Google Scholar
    There is no corresponding record for this reference.
  18. 18
    Hsieh, J. C.; Yun, D. S.; Hu, E.; Belcher, A. M. J. Mater. Chem. 2010, 20, 1435,  DOI: 10.1039/b922196d
    Google Scholar
    There is no corresponding record for this reference.
  19. 19
    Choi, J.; Gillan, E. G. J. Mater. Chem. 2006, 16, 3774,  DOI: 10.1039/B608204A
    Google Scholar
    There is no corresponding record for this reference.
  20. 20
    Miura, A.; Takei, T.; Kumada, N. Cryst. Growth Des. 2012, 12, 4545,  DOI: 10.1021/cg3007266
    Google Scholar
    20
    Synthesis of Wurtzite-Type InN Crystals by Low-Temperature Nitridation of LiInO2 Using NaNH2 Flux
    Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro
    Crystal Growth & Design (2012), 12 (9), 4545-4547CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
    Nitridation of oxides >500° is a conventional route for the synthesis of various oxynitrides and nitrides. However, this technique has the disadvantages of requiring a high temp. to break the strong metal and O bonds and of low use efficiency of N sources such as toxic NH3. Here, the authors show a simple low-temp. synthesis of InN nanocrystals via the nitridation of LiInO2 by NaNH2 flux at 240° in a Teflon-lined autoclave. The NaNH2 flux converted irregular-shaped LiInO2 powder to 50-300 nm InN nanocrystals with well-developed facets. The product crystd. in the hexagonal wurtzite structure with lattice parameters of a 3.545 and c 5.717 Å. Li in the starting oxide is essential for this low-temp. nitridation.
  21. 21
    Zhao, S.; Fathololoumi, S.; Bevan, K. H.; Liu, D. P.; Kibria, M. G.; Li, Q.; Wang, G. T.; Guo, H.; Mi, Z. Nano Lett. 2012, 12, 2877,  DOI: 10.1021/nl300476d
    Google Scholar
    There is no corresponding record for this reference.
  22. 22
    Tessarek, C.; Fladischer, S.; Dieker, C.; Sarau, G.; Hoffmann, B.; Bashouti, M.; Göbelt, M.; Heilmann, M.; Latzel, M.; Butzen, E.; Figge, S.; Gust, A.; Höflich, K.; Feichtner, T.; Büchele, M.; Schwarzburg, K.; Spiecker, E.; Christiansen, S. Nano Lett. 2016, 16, 3415,  DOI: 10.1021/acs.nanolett.5b03889
    Google Scholar
    22
    Self-Catalyzed Growth of Vertically Aligned InN Nanorods by Metal-Organic Vapor Phase Epitaxy
    Tessarek, C.; Fladischer, S.; Dieker, C.; Sarau, G.; Hoffmann, B.; Bashouti, M.; Goebelt, M.; Heilmann, M.; Latzel, M.; Butzen, E.; Figge, S.; Gust, A.; Hoeflich, K.; Feichtner, T.; Buechele, M.; Schwarzburg, K.; Spiecker, E.; Christiansen, S.
    Nano Letters (2016), 16 (6), 3415-3425CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
    Vertically aligned hexagonal InN nanorods were grown mask-free by conventional OMVPE without any foreign catalyst. The In droplets on top of the nanorods indicate a self-catalytic vapor-liq.-solid growth mode. A systematic study on important growth parameters was carried out for the optimization of nanorod morphol. The nanorod N-polarity, induced by high temp. nitridation of the Al2O3 substrate, is necessary to achieve vertical growth. H2, usually inapplicable during InN growth due to formation of metallic In, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the Al2O3 surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temp. is similar. TEM, spatially resolved energy-dispersive x-ray spectroscopy, X-ray diffraction, XPS, and Raman spectroscopy were performed to analyze the structural properties. Spatially resolved cathodoluminescence studies are carried out to verify the optical activity of the InN nanorods.
  23. 23
    Kortshagen, U. J. Phys. D: Appl. Phys. 2009, 42, 113001,  DOI: 10.1088/0022-3727/42/11/113001
    Google Scholar
    23
    Nonthermal plasma synthesis of semiconductor nanocrystals
    Kortshagen, Uwe
    Journal of Physics D: Applied Physics (2009), 42 (11), 113001/1-113001/22CODEN: JPAPBE; ISSN:0022-3727. (Institute of Physics Publishing)
    A review, with 166 refs. Semiconductor nanocrystals have attracted considerable interest for a wide range of applications including light-emitting devices and displays, photovoltaic cells, nanoelectronic circuit elements, thermoelec. energy generation and luminescent markers in biomedicine. A particular advantage of semiconductor nanocrystals compared with bulk materials rests in their size-tunable optical, mech. and thermal properties. While nanocrystals of ionically bonded semiconductors can conveniently be synthesized with liq. phase chem., covalently bonded semiconductors require higher synthesis temps. Over the past decade, nonthermal plasmas have emerged as capable synthetic approaches for the covalently bonded semiconductor nanocrystals. Among the main advantages of nanocrystal synthesis in plasmas is the unipolar elec. charging of nanocrystals that helps avoid or reduce particle agglomeration and the selective heating of nanoparticles immersed in low-pressure plasmas. This paper discusses the important fundamental mechanisms of nanocrystal formation in plasmas, reviews the range of synthesis approaches reported in the literature and discusses some of the potential applications of plasma-synthesized semiconductor nanocrystals.
  24. 24
    Dixit, A.; Sudakar, J. S.; Thakur, K.; Padmanabhan, S.; Kumar, R.; Naik, R.; Naik, V. M.; Lawes, G. J. Appl. Phys. 2009, 105, 053104,  DOI: 10.1063/1.3088879
    Google Scholar
    24
    Strong plasmon absorption in InN thin films
    Dixit, A.; Sudakar, C.; Thakur, J. S.; Padmanabhan, K.; Kumar, Sanjiv; Naik, R.; Naik, V. M.; Lawes, G.
    Journal of Applied Physics (2009), 105 (5), 053104/1-053104/5CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
    The authors have fabricated InN thin films using radiofrequency magnetron sputtering from an In metal target. Optical and elec. measurements show that these as-grown films are n-type with carrier concns. ranging from 1020 to 1021 cm-3. This variation in carrier d. is produced by controlling the conditions during the deposition. The authors used Rutherford backscattering spectrometry to identify possible sources for n-type carriers. In addn. to strong direct bandgap optical absorption ranging from 1.4 to 2.0 eV, a large plasmon absorption peak in the IR region (0.45-0.8 eV) is also obsd. This tunable IR absorption suggests that these highly degenerate InN films could be used for a no. of applications, including optical filters and IR devices. (c) 2009 American Institute of Physics.
  25. 25
    Naik, V. M.; Naik, R.; Haddad, D. B.; Thakur, J. S.; Auner, G. W.; Lu, H.; Schaff, W. J. Appl. Phys. Lett. 2005, 86, 201913,  DOI: 10.1063/1.1935031
    Google Scholar
    There is no corresponding record for this reference.
  26. 26
    Palomaki, P. K. B.; Miller, E. M.; Neale, N. R. J. Am. Chem. Soc. 2013, 135, 14142,  DOI: 10.1021/ja404599g
    Google Scholar
    There is no corresponding record for this reference.
  27. 27
    Luther, J. M.; Jain, P. K.; Ewers, T.; Alivisatos, A. P. Nat. Mater. 2011, 10, 361,  DOI: 10.1038/nmat3004
    Google Scholar
    27
    Localized surface plasmon resonances arising from free carriers in doped quantum dots
    Luther, Joseph M.; Jain, Prashant K.; Ewers, Trevor; Alivisatos, A. Paul
    Nature Materials (2011), 10 (5), 361-366CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
    Localized surface plasmon resonances (LSPRs) typically arise in nanostructures of noble metals resulting in enhanced and geometrically tunable absorption and scattering resonances. LSPRs are not limited to nanostructures of metals and can also be achieved in semiconductor nanocrystals with appreciable free carrier concns. Defined LSPRs arising from p-type carriers in vacancy-doped semiconductor quantum dots (QDs) are described. Achievement of LSPRs by free carrier doping of a semiconductor nanocrystal would allow active on-chip control of LSPR responses. Plasmonic sensing and manipulation of solid-state processes in single nanocrystals constitutes another interesting possibility. Doped semiconductor QDs allow realization of LSPRs and quantum-confined excitons within the same nanostructure, opening up the possibility of strong coupling of photonic and electronic modes, with implications for light harvesting, nonlinear optics, and quantum information processing.
  28. 28
    Klar, T.; Perner, M.; Grosse, S.; von Plessen, G.; Spirkl, W.; Feldmann, J. Phys. Rev. Lett. 1998, 80, 4249,  DOI: 10.1103/PhysRevLett.80.4249
    Google Scholar
    There is no corresponding record for this reference.
  29. 29
    Greenberg, B. L.; Ganguly, S.; Held, J. T.; Kramer, N. J.; Mkhoyan, K. A.; Aydil, E. S.; Kortshagen, E. S. Nano Lett. 2015, 15, 8162,  DOI: 10.1021/acs.nanolett.5b03600
    Google Scholar
    There is no corresponding record for this reference.
  30. 30
    Lounis, S. D.; Runnerstrom, E. L.; Bergerud, A.; Nordlund, D.; Milliron, D. J. J. Am. Chem. Soc. 2014, 136, 7110,  DOI: 10.1021/ja502541z
    Google Scholar
    30
    Influence of Dopant Distribution on the Plasmonic Properties of Indium Tin Oxide Nanocrystals
    Lounis, Sebastien D.; Runnerstrom, Evan L.; Bergerud, Amy; Nordlund, Dennis; Milliron, Delia J.
    Journal of the American Chemical Society (2014), 136 (19), 7110-7116CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Doped metal oxide nanocrystals represent an exciting frontier for colloidal synthesis of plasmonic materials, displaying unique optoelectronic properties and showing promise for a variety of applications. However, fundamental questions about the nature of doping in these materials remain. In this article, the strong influence of radial dopant distribution on the optoelectronic properties of colloidal indium tin oxide nanocrystals is reported. Comparing elemental depth-profiling by XPS with detailed modeling and simulation of the optical extinction of these nanocrystals using the Drude model for free electrons, a correlation between surface segregation of tin ions and the av. activation of dopants is obsd. A strong influence of surface segregation of tin on the line shape of the localized surface plasmon resonance (LSPR) is also reported. Samples with tin segregated near the surface show a sym. line shape that suggests weak or no damping of the plasmon by ionized impurities. It is suggested that segregation of tin near the surface facilitates compensation of the dopant ions by electronic defects and oxygen interstitials, thus reducing activation. A core-shell model is proposed to explain the obsd. differences in line shape. These results demonstrate the nuanced role of dopant distribution in detg. the optoelectronic properties of semiconductor nanocrystals and suggest that more detailed study of the distribution and structure of defects in plasmonic colloidal nanocrystals is warranted.
  31. 31
    Runnerstrom, E. L.; Bergerud, A.; Agrawal, A.; Johns, R. W.; Dahlman, C. J.; Singh, A.; Selbach, S. M.; Milliron, D. J. Nano Lett. 2016, 16, 3390,  DOI: 10.1021/acs.nanolett.6b01171
    Google Scholar
    There is no corresponding record for this reference.
  32. 32
    Ye, X.; Fei, J.; Diroll, B. T.; Paik, T.; Murray, C. B. J. Am. Chem. Soc. 2014, 136, 11680,  DOI: 10.1021/ja5039903
    Google Scholar
    There is no corresponding record for this reference.
  33. 33
    Wu, J.; Walukiewicz, W.; Shan, W.; Yu, K. M.; Ager, J. W.; Haller, E. E.; Lu, H.; Schaff, W. Phys. Rev. B: Condens. Matter Mater. Phys. 2002, 66, 201403,  DOI: 10.1103/PhysRevB.66.201403
    Google Scholar
    There is no corresponding record for this reference.
  34. 34
    Maruska, H. P.; Tietjen, J. J. Appl. Phys. Lett. 1969, 15, 327,  DOI: 10.1063/1.1652845
    Google Scholar
    There is no corresponding record for this reference.
  35. 35
    Ganchenkova, M. G.; Nieminen, R. M. Phys. Rev. Lett. 2006, 96, 196402,  DOI: 10.1103/PhysRevLett.96.196402
    Google Scholar
    There is no corresponding record for this reference.
  36. 36
    Piper, L. F. J.; Veal, T. D.; McConville, C. F.; Lu, H.; Schaff, W. J. Appl. Phys. Lett. 2006, 88, 252109,  DOI: 10.1063/1.2214156
    Google Scholar
    There is no corresponding record for this reference.
  37. 37
    Pilch, I.; Söderström, D.; Hasan, M. I.; Helmersson, U.; Brenning, N. Appl. Phys. Lett. 2013, 103, 193108,  DOI: 10.1063/1.4828883
    Google Scholar
    There is no corresponding record for this reference.
  38. 38
    Hasan, M. I.; Pilch, I.; Soderstrom, D.; Lundin, D.; Helmersson, U.; Brenning, N. Plasma Sources Sci. Technol. 2013, 22, 035006,  DOI: 10.1088/0963-0252/22/3/035006
    Google Scholar
    38
    Modeling the extraction of sputtered metal from high power impulse hollow cathode discharges
    Hasan, M. I.; Pilch, I.; Soederstroem, D.; Lundin, D.; Helmersson, U.; Brenning, N.
    Plasma Sources Science & Technology (2013), 22 (3), 035006/1-035006/12, 12 pp.CODEN: PSTEEU; ISSN:1361-6595. (IOP Publishing Ltd.)
    High power impulse hollow cathode sputtering is studied as a means to produce high fluxes of neutral and ionized sputtered metal species. A model is constructed for the understanding and optimization of such discharges. It relates input parameters such as the geometry of the cathode, the elec. pulse form and frequency, and the feed gas flow rate and pressure, to the prodn., ionization, temp. and extn. of the sputtered species. Examples of processes that can be quantified by the use of the model are the internal prodn. of sputtered metal and the degree of its ionization, the speed and efficiency of out-puffing from the hollow cathode assocd. with the pulses, and the gas back-flow into the hollow cathode between pulses. The use of the model is exemplified with a special case where the aim is the synthesis of nanoparticles in an expansion vol. that lies outside the hollow cathode itself. The goals are here a max. extn. efficiency, and a high degree of ionization of the sputtered metal. It is demonstrated that it is possible to reach a degree of ionization above 85%, and extn. efficiencies of 3% and 17% for the neutral and ionized sputtered components, resp.
  39. 39
    Rauch, C.; Tuomisto, F.; King, P. D. C.; Veal, T. D.; Lu, H.; Schaff, W. J. Appl. Phys. Lett. 2012, 101, 011903,  DOI: 10.1063/1.4732508
    Google Scholar
    There is no corresponding record for this reference.
  40. 40
    Look, D. C. Appl. Phys. Lett. 2002, 80, 258,  DOI: 10.1063/1.1432742
    Google Scholar
    There is no corresponding record for this reference.
  41. 41
    Duan, X. M.; Stampfl, C. Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 77, 115207,  DOI: 10.1103/PhysRevB.77.115207
    Google Scholar
    There is no corresponding record for this reference.
  42. 42
    Jones, R. E.; Li, S. X.; Hsu, L.; Yu, K. M.; Walukiewicz, W.; Liliental-Weber, Z.; Ager, J. W.; Haller, E. E.; Lu, H.; Schaff, W. J. Phys. B 2006, 376-377, 436,  DOI: 10.1016/j.physb.2005.12.112
    Google Scholar
    42
    Native-defect-controlled n-type conductivity in InN
    Jones, R. E.; Li, S. X.; Hsu, L.; Yu, K. M.; Walukiewicz, W.; Liliental-Weber, Z.; Ager, J. W., III; Haller, E. E.; Lu, H.; Schaff, W. J.
    Physica B: Condensed Matter (Amsterdam, Netherlands) (2006), 376-377 (), 436-439CODEN: PHYBE3; ISSN:0921-4526. (Elsevier B.V.)
    High-energy particle irradn. was shown previously to be a method for n-type doping of InN. Here we irradiated InN with H+ and He+ particles to study the dependence of the electron mobility on electron concns. varying from mid-1018 to mid-1020 cm-3. We find that the electron mobility is limited by scattering from the ionized defects created by irradn., resulting in a strong correlation between mobility and electron concn. Furthermore, our calcns. suggest that the radiation-induced defects may be triply charged donors.

Cited By

Click to copy section linkSection link copied!
Citation Statements
Explore this article's citation statements on scite.ai
powered by  Scite

This article is cited by 27 publications.

  1. Fernando M. de Oliveira, Andrian V. Kuchuk, Petro M. Lytvyn, Cosmin Romanitan, Hryhorii V. Stanchu, Marcio D. Teodoro, Morgan E. Ware, Yuriy I. Mazur, Gregory J. Salamo. Electron Accumulation Tuning by Surface-to-Volume Scaling of Nanostructured InN Grown on GaN(001) for Narrow-Bandgap Optoelectronics. ACS Applied Nano Materials 2023, 6 (9) , 7582-7592. https://doi.org/10.1021/acsanm.3c00732
  2. Yao Lu, Tsz Him Chow, Ka Kit Chui, Jianfang Wang. Electromagnetic Resonance in Organic Conductive Polymers. The Journal of Physical Chemistry C 2023, 127 (12) , 5643-5652. https://doi.org/10.1021/acs.jpcc.3c00249
  3. Krishna Chand Maurya, Abhijit Chatterjee, Sonnada Math Shivaprasad, Bivas Saha. Morphology-Controlled Reststrahlen Band and Infrared Plasmon Polariton in GaN Nanostructures. Nano Letters 2022, 22 (23) , 9606-9613. https://doi.org/10.1021/acs.nanolett.2c03748
  4. Mahmoud Sayed, Jiaguo Yu, Gang Liu, Mietek Jaroniec. Non-Noble Plasmonic Metal-Based Photocatalysts. Chemical Reviews 2022, 122 (11) , 10484-10537. https://doi.org/10.1021/acs.chemrev.1c00473
  5. Nitu Syed, Alastair Stacey, Ali Zavabeti, Chung Kim Nguyen, Benedikt Haas, Christoph T. Koch, Daniel L. Creedon, Enrico Della Gaspera, Philipp Reineck, Azmira Jannat, Matthias Wurdack, Sarah E. Bamford, Paul J. Pigram, Sherif Abdulkader Tawfik, Salvy P. Russo, Billy J. Murdoch, Kourosh Kalantar-Zadeh, Chris F. McConville, Torben Daeneke. Large Area Ultrathin InN and Tin Doped InN Nanosheets Featuring 2D Electron Gases. ACS Nano 2022, 16 (4) , 5476-5486. https://doi.org/10.1021/acsnano.1c09636
  6. Mengqi Sun, Nicholas Kreis, Kexun Chen, Xiaoqi Fu, Song Guo, Hui Wang. Covellite Nanodisks and Digenite Nanorings: Colloidal Synthesis, Phase Transitions, and Optical Properties. Chemistry of Materials 2021, 33 (21) , 8546-8558. https://doi.org/10.1021/acs.chemmater.1c03259
  7. Yaxu Zhong, Zeke Liu, Erik Sarnello, Tao Li, Yang Liu, Jun Chen, Xingchen Ye. Controlling Infrared Plasmon Resonances in Inverse-Spinel Cadmium Stannate Nanocrystals via Site-Selective Cation-Exchange Reactions. Chemistry of Materials 2021, 33 (6) , 1954-1963. https://doi.org/10.1021/acs.chemmater.0c03176
  8. Emanuele Poliani, Daniel Seidlitz, Maximilian Ries, Soo J. Choi, James S. Speck, Axel Hoffmann, Markus R. Wagner. Strong Near-Field Light–Matter Interaction in Plasmon-Resonant Tip-Enhanced Raman Scattering in Indium Nitride. The Journal of Physical Chemistry C 2020, 124 (51) , 28178-28185. https://doi.org/10.1021/acs.jpcc.0c04549
  9. Yasuhiro Kuranaga, Hiroaki Matsui, Akifumi Ikehata, Yuta Shimoda, Makoto Noiri, Ya-Lun Ho, Jean-Jacques Delaunay, Yuji Teramura, Hitoshi Tabata. Enhancing Detection Sensitivity of ZnO-Based Infrared Plasmonic Sensors Using Capped Dielectric Ga2O3 Layers for Real-Time Monitoring of Biological Interactions. ACS Applied Bio Materials 2020, 3 (9) , 6331-6342. https://doi.org/10.1021/acsabm.0c00792
  10. Zeke Liu, Yaxu Zhong, Ibrahim Shafei, Soojin Jeong, Liguang Wang, Hoai T. Nguyen, Cheng-Jun Sun, Tao Li, Jun Chen, Lei Chen, Yaroslav Losovyj, Xinfeng Gao, Wanli Ma, Xingchen Ye. Broadband Tunable Mid-infrared Plasmon Resonances in Cadmium Oxide Nanocrystals Induced by Size-Dependent Nonstoichiometry. Nano Letters 2020, 20 (4) , 2821-2828. https://doi.org/10.1021/acs.nanolett.0c00542
  11. Necip B. Uner, Dariusz M. Niedzwiedzki, Elijah Thimsen. Nonequilibrium Plasma Aerotaxy of InN Nanocrystals and Their Photonic Properties. The Journal of Physical Chemistry C 2019, 123 (50) , 30613-30622. https://doi.org/10.1021/acs.jpcc.9b09555
  12. Junling Qu, Clément Livache, Bertille Martinez, Charlie Gréboval, Audrey Chu, Elisa Meriggio, Julien Ramade, Hervé Cruguel, Xiang Zhen Xu, Anna Proust, Florence Volatron, Gregory Cabailh, Nicolas Goubet, Emmanuel Lhuillier. Transport in ITO Nanocrystals with Short- to Long-Wave Infrared Absorption for Heavy-Metal-Free Infrared Photodetection. ACS Applied Nano Materials 2019, 2 (3) , 1621-1630. https://doi.org/10.1021/acsanm.9b00067
  13. Sathish Shanmugam, Francesco Barbero, Aurora Bellone, Alessia Giovanna Santa Banche Niclot, Simone Miatto, Guido Perrone, Katia Mareschi, Ivana Fenoglio. Enhancing the translational potential of photo-responsive covellite in medicine: solvent-free tuning of CuS nanoparticles LSPR and control of their stability in aqueous media by a carbonaceous shell. Materials Today Chemistry 2025, 46 , 102765. https://doi.org/10.1016/j.mtchem.2025.102765
  14. Xiaolei Liu, Baibiao Huang, Juan Li, Baojun Li, Zaizhu Lou. Full-spectrum plasmonic semiconductors for photocatalysis. Materials Horizons 2024, 11 (22) , 5470-5498. https://doi.org/10.1039/D4MH00515E
  15. Shuming Li, Heng Rao, Chenxi Tang, Tengfei Bao, Ping She, Jun-sheng Qin. Recent advances of non-noble metals based plasma materials in photocatalysis. Coordination Chemistry Reviews 2024, 510 , 215803. https://doi.org/10.1016/j.ccr.2024.215803
  16. He Li, Sadegh Askari, Jihao Wang, Niklas Wolff, Malte Behrens, Lorenz Kienle, Jan Benedikt. Nitrogen-doped NiCo2O4 nanowires on carbon paper as a self-supported air cathode for rechargeable Zn-air batteries. International Journal of Hydrogen Energy 2023, 48 (67) , 26107-26118. https://doi.org/10.1016/j.ijhydene.2023.03.146
  17. Ghenadii Korotcenkov, Denis L. Nika. Hg-Based Narrow Bandgap II-VI Semiconductors. 2023, 67-86. https://doi.org/10.1007/978-3-031-19531-0_3
  18. Sourav Rej, Eva Yazmin Santiago, Olga Baturina, Yu Zhang, Sven Burger, Stěpán Kment, Alexander O. Govorov, Alberto Naldoni. Colloidal titanium nitride nanobars for broadband inexpensive plasmonics and photochemistry from visible to mid-IR wavelengths. Nano Energy 2022, 104 , 107989. https://doi.org/10.1016/j.nanoen.2022.107989
  19. Hongbin Yang, Andrea Konečná, Xianghan Xu, Sang‐Wook Cheong, Eric Garfunkel, F. Javier García de Abajo, Philip E. Batson. Low‐Loss Tunable Infrared Plasmons in the High‐Mobility Perovskite (Ba,La)SnO 3. Small 2022, 18 (16) https://doi.org/10.1002/smll.202106897
  20. Kefeng Wu, Siyu Huang, Wenliang Wang, Guoqiang Li. Recent progress in III-nitride nanosheets: properties, materials and applications. Semiconductor Science and Technology 2021, 36 (12) , 123002. https://doi.org/10.1088/1361-6641/ac2c26
  21. Juan Li, Zaizhu Lou, Baojun Li. Engineering plasmonic semiconductors for enhanced photocatalysis. Journal of Materials Chemistry A 2021, 9 (35) , 18818-18835. https://doi.org/10.1039/D1TA04541E
  22. Mengxia Liu, Nuri Yazdani, Maksym Yarema, Maximilian Jansen, Vanessa Wood, Edward H. Sargent. Colloidal quantum dot electronics. Nature Electronics 2021, 4 (8) , 548-558. https://doi.org/10.1038/s41928-021-00632-7
  23. Hui Li, Heng Zhang, Hao Wu, Jiaming Hao, Chang Liu. Tree-like structures of InN nanoparticles on agminated anodic aluminum oxide by plasma-assisted reactive evaporation. Applied Surface Science 2020, 503 , 144309. https://doi.org/10.1016/j.apsusc.2019.144309
  24. S. Askari, H. Machhadani, J. Benedikt, U. Helmersson. Plasma-based processes for planar and 3D surface patterning of functional nanoparticles. Journal of Nanoparticle Research 2019, 21 (11) https://doi.org/10.1007/s11051-019-4674-3
  25. Wenqing Song, Jiawei Si, Shaoteng Wu, Zelin Hu, Linyun Long, Tao Li, Xiang Gao, Lei Zhang, Wenhui Zhu, Liancheng Wang. Synthesis and morphology evolution of indium nitride (InN) nanotubes and nanobelts by chemical vapor deposition. CrystEngComm 2019, 21 (35) , 5356-5362. https://doi.org/10.1039/C9CE00975B
  26. Wenqing Xie, Gongxun Bai, Yangjian Cai, Ying Tian, Feifei Huang, Shiqing Xu, Junjie Zhang. Polarization-assisted energy transfer process to improve mid-infrared luminescence by tuning nano-structure in Dy3+/Er3+ co-doped borate glass ceramics system. Journal of Alloys and Compounds 2019, 788 , 972-977. https://doi.org/10.1016/j.jallcom.2019.02.320
  27. Clément Livache, Bertille Martinez, Nicolas Goubet, Julien Ramade, Emmanuel Lhuillier. Road Map for Nanocrystal Based Infrared Photodetectors. Frontiers in Chemistry 2018, 6 https://doi.org/10.3389/fchem.2018.00575
Download PDF
Go to Nano Letters
Get e-Alerts
Get e-Alerts

Nano Letters

Cite this: Nano Lett. 2018, 18, 9, 5681–5687
Click to copy citationCitation copied!
https://doi.org/10.1021/acs.nanolett.8b02260
Published August 23, 2018

Copyright © 2018 American Chemical Society. This publication is licensed under CC-BY.

Article Views

1992

Altmetric

-

Citations

27
Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. (a) Pulsed plasma process for controlled growth of nanocrystals (NCs). The generated plasma is highly ionized and lead to high growth rates by collecting ions into the negatively charged NCs. Eimp denotes the kinetic energy of ions impinging on the NC. (b) Nanocrystal diameter and corresponding nitrogen deficiency for NCs produced by varying the average plasma power; error bars for the nitrogen deficiency represents the standard error of the mean value and for the NC diameter represents the standard deviation of the distribution for the corresponding mean value. (c) Typical XRD and SEM image (inset) of wurtzite InN NCs.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. (a) The FTIR spectra of the InN nanocrystals for a range of nitrogen deficiencies, InN1–x, 0.017 < x < 0.085. The absorption peak is shifted to higher energies in nanocrystals with higher nitrogen deficiency. (b) Free-electron concentration, damping factor, and optically calculated free electron mobility as a function of nitrogen deficiency in InN nanocrystals.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. (a) XPS valence band spectra of InN nanocrystals with different nitrogen deficiency, InN1–x, 0.017 < x < 0.085. The difference between the valence band maximum and Fermi level is increased in nanocrystals with higher nitrogen deficiency. (b) The optical bandgap in InN nanocrystals as a function of nitrogen deficiency is obtained from the ultraviolet–visible absorption measurements, XPS measurements (panel a) and calculated from Kane model. (c) Modulating free-electron concentration and Fermi level in degenerate InN1–x nanocrystals. The right panel shows localized surface plasmon frequency versus free-electron concentration. The technically important infrared ranges of spectrum are shown NIR (near-infrared), MWIR (midwave infrared), and LWIR (long-wave infrared).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. (a) Concentration of donor and acceptor nitrogen vacancy defects in InN nanocrystals (see SI for details). (b) Calculated mobility limited by ionized defect centers in InN presented as a function of electron concentration.

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    This article references 42 other publications.

    1. 1
      Rodrigo, D.; Limaj, O.; Janner, D.; Etezadi, D.; García de Abajo, F. J.; Pruneri, V.; Altug, H. Science 2015, 349, 165,  DOI: 10.1126/science.aab2051
      1
      Mid-infrared plasmonic biosensing with graphene
      Rodrigo, Daniel; Limaj, Odeta; Janner, Davide; Etezadi, Dordaneh; Garcia de Abajo, F. Javier; Pruneri, Valerio; Altug, Hatice
      Science (Washington, DC, United States) (2015), 349 (6244), 165-168CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      IR spectroscopy is the technique of choice for chem. identification of biomols. through their vibrational fingerprints. However, IR light interacts poorly with nanometric-size mols. The authors exploit the unique electrooptical properties of graphene to demonstrate a high-sensitivity tunable plasmonic biosensor for chem. specific label-free detection of protein monolayers. The plasmon resonance of nanostructured graphene is dynamically tuned to selectively probe the protein at different frequencies and ext. its complex refractive index. Addnl., the extreme spatial light confinement in graphene, up to two orders of magnitude higher than in metals, produces an unprecedentedly high overlap with nanometric biomols., enabling superior sensitivity in the detection of their refractive index and vibrational fingerprints. The combination of tunable spectral selectivity and enhanced sensitivity of graphene opens exciting prospects for biosensing.
    2. 2
      Stanley, R. Nat. Photonics 2012, 6, 409,  DOI: 10.1038/nphoton.2012.161
      2
      Plasmonics in the mid-infrared
      Stanley, Ross
      Nature Photonics (2012), 6 (7), 409-411CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)
      A review. Plasmonics can be used to enhance mid-IR sources, sensors and detectors for applications such as chem. sensing, thermal imaging and heat scavenging. The challenge now is to integrate these technologies in cost-effective, compact and reliable platforms.
    3. 3
      Neubrech, F.; Huck, C.; Weber, K.; Pucci, A.; Giessen, H. Chem. Rev. 2017, 117, 5110,  DOI: 10.1021/acs.chemrev.6b00743
      3
      Surface-Enhanced Infrared Spectroscopy Using Resonant Nanoantennas
      Neubrech, Frank; Huck, Christian; Weber, Ksenia; Pucci, Annemarie; Giessen, Harald
      Chemical Reviews (Washington, DC, United States) (2017), 117 (7), 5110-5145CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      IR spectroscopy is a powerful tool widely used in research and industry for a label-free and unambiguous identification of mol. species. Inconveniently, its application to spectroscopic anal. of minute amts. of materials, for example, in sensing applications, is hampered by the low IR absorption cross-sections. Surface-enhanced IR spectroscopy using resonant metal nanoantennas, or short "resonant SEIRA", overcomes this limitation. Resonantly excited, such metal nanostructures feature collective oscillations of electrons (plasmons), providing huge electromagnetic fields on the nanometer scale. IR vibrations of mols. located in these fields are enhanced by orders of magnitude enabling a spectroscopic characterization with unprecedented sensitivity. In this Review, we introduce the concept of resonant SEIRA and discuss the underlying physics, particularly, the resonant coupling between mol. and antenna excitations as well as the spatial extent of the enhancement and its scaling with frequency. On the basis of these fundamentals, different routes to maximize the SEIRA enhancement are reviewed including the choice of nanostructures geometries, arrangements, and materials. Furthermore, first applications such as the detection of proteins, the monitoring of dynamic processes, and hyperspectral IR chem. imaging are discussed, demonstrating the sensitivity and broad applicability of resonant SEIRA.
    4. 4
      Clavero, C. Nat. Photonics 2014, 8, 95,  DOI: 10.1038/nphoton.2013.238
      4
      Plasmon-induced hot-electron generation at nanoparticle/metal-oxide interfaces for photovoltaic and photocatalytic devices
      Clavero, Cesar
      Nature Photonics (2014), 8 (2), 95-103CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)
      A review. Finding higher efficiency schemes for electron-hole sepn. is of paramount importance for realizing more efficient conversion of solar energy in photovoltaic and photocatalytic devices. Plasmonic energy conversion has been proposed as a promising alternative to conventional electron-hole sepn. in semiconductor devices. This emerging method is based on the generation of hot electrons in plasmonic nanostructures through electromagnetic decay of surface plasmons. Here, the fundamentals of hot-electron generation, injection and regeneration are reviewed, with special attention paid to recent progress towards photovoltaic devices. This new energy-conversion method potentially offers high conversion efficiencies, while keeping fabrication costs low. However, several considerations regarding the materials, architectures and fabrication methods used need to be carefully evaluated to advance this field.
    5. 5
      Tittl, A.; Michel, A. K.; Schäferling, M.; Yin, X.; Gholipour, B.; Cui, L.; Wuttig, M.; Taubner, T.; Neubrech, F.; Giessen, H. Adv. Mater. 2015, 27, 4597,  DOI: 10.1002/adma.201502023
      There is no corresponding record for this reference.
    6. 6
      Yan, H.; Low, T.; Zhu, W.; Wu, Y.; Freitag, M.; Li, X.; Guinea, F.; Avouris, P.; Xia, F. Nat. Photonics 2013, 7, 394,  DOI: 10.1038/nphoton.2013.57
      6
      Damping pathways of mid-infrared plasmons in graphene nanostructures
      Yan, Hugen; Low, Tony; Zhu, Wenjuan; Wu, Yanqing; Freitag, Marcus; Li, Xuesong; Guinea, Francisco; Avouris, Phaedon; Xia, Fengnian
      Nature Photonics (2013), 7 (5), 394-399CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)
      Plasmon is the quantum of the collective oscillation of electrons. How plasmon loses its energy (or damping) plays a pivotal role in plasmonic science and technol. Graphene plasmon is of particular interest, partly because of its potentially low damping rate. However, to date, damping pathways have not been clearly unravelled exptl. Here, we demonstrate mid-IR (4-15 μm) plasmons in graphene nanostructures with dimensions as small as 50 nm (with a mode area of ∼1 × 10-3 μm2). We also reveal damping channels via graphene intrinsic optical phonons and scattering from the edges. Plasmon lifetimes of 20 fs or less are obsd. when damping via the emission of graphene optical phonons is allowed. Furthermore, surface polar phonons in the SiO2 substrate under graphene nanostructures lead to a significantly modified plasmon dispersion and damping, in contrast to the case of a nonpolar diamond-like-carbon substrate. Our study paves the way for applications of graphene in plasmonic waveguides, modulators and detectors from sub-terahertz to mid-IR regimes.
    7. 7
      Naik, G. V.; Shalaev, V. M.; Boltasseva, A. Adv. Mater. 2013, 25, 3264,  DOI: 10.1002/adma.201205076
      7
      Alternative Plasmonic Materials: Beyond Gold and Silver
      Naik, Gururaj V.; Shalaev, Vladimir M.; Boltasseva, Alexandra
      Advanced Materials (Weinheim, Germany) (2013), 25 (24), 3264-3294CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Materials research plays a vital role in transforming breakthrough scientific ideas into next-generation technol. Similar to the way Si revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research in plasmonics and metamaterials lacks good material building blocks to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, esp. metals. There are many materials, other than conventional metallic components such as Au and Ag, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2-dimensional materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions.
    8. 8
      Mattox, T. M.; Ye, X.; Manthiram, K.; Schuck, P. J.; Alivisatos, A. P.; Urban, J. J. Adv. Mater. 2015, 27, 5830,  DOI: 10.1002/adma.201502218
      There is no corresponding record for this reference.
    9. 9
      Wagner, M.; McLeod, A. S.; Maddox, S. J.; Fei, Z.; Liu, M.; Averitt, R. D.; Fogler, M. M.; Bank, S. R.; Keilmann, F.; Basov, D. N. Nano Lett. 2014, 14, 4529,  DOI: 10.1021/nl501558t
      There is no corresponding record for this reference.
    10. 10
      Khurgin, J. b. Nat. Nanotechnol. 2015, 10, 2,  DOI: 10.1038/nnano.2014.310
      10
      How to deal with the loss in plasmonics and metamaterials
      Khurgin, Jacob B.
      Nature Nanotechnology (2015), 10 (1), 2-6CODEN: NNAABX; ISSN:1748-3387. (Nature Publishing Group)
      A review with commentary. Metal losses affect the performance of every plasmonic or metamaterial structure; dealing with them will det. the degree to which these structures will find practical applications.
    11. 11
      Law, S.; Podolskiy, V.; Wasserman, D. Nanophotonics 2013, 2, 103,  DOI: 10.1515/nanoph-2012-0027
      There is no corresponding record for this reference.
    12. 12
      Sachet, E.; Shelton, C. T.; Harris, J. S.; Gaddy, B. E.; Irving, D. L.; Curtarolo, S.; Donovan, B. F.; Hopkins, P. E.; Sharma, P. A.; Sharma, A. L.; Ihlefeld, J.; Franzen, S.; Maria, J.-P. Nat. Mater. 2015, 14, 414,  DOI: 10.1038/nmat4203
      12
      Dysprosium-doped cadmium oxide as a gateway material for mid-infrared plasmonics
      Sachet, Edward; Shelton, Christopher T.; Harris, Joshua S.; Gaddy, Benjamin E.; Irving, Douglas L.; Curtarolo, Stefano; Donovan, Brian F.; Hopkins, Patrick E.; Sharma, Peter A.; Sharma, Ana Lima; Ihlefeld, Jon; Franzen, Stefan; Maria, Jon-Paul
      Nature Materials (2015), 14 (4), 414-420CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      The interest in plasmonic technologies surrounds many emergent optoelectronic applications, such as plasmon lasers, transistors, sensors and information storage. Although plasmonic materials for UV-visible and near-IR wavelengths have been found, the mid-IR range remains a challenge to address: few known systems can achieve subwavelength optical confinement with low loss in this range. With a combination of expts. and ab initio modeling, here we demonstrate an extreme peak of electron mobility in Dy-doped CdO that is achieved through accurate 'defect equil. engineering'. In so doing, we create a tunable plasmon host that satisfies the criteria for mid-IR spectrum plasmonics, and overcomes the losses seen in conventional plasmonic materials. In particular, extrinsic doping pins the CdO Fermi level above the conduction band min. and it increases the formation energy of native oxygen vacancies, thus reducing their populations by several orders of magnitude. The substitutional lattice strain induced by Dy doping is sufficiently small, allowing mobility values around 500 cm2 V-1 s-1 for carrier densities above 1020 cm-3. Our work shows that CdO:Dy is a model system for intrinsic and extrinsic manipulation of defects affecting elec., optical and thermal properties, that oxide conductors are ideal candidates for plasmonic devices and that the defect engineering approach for property optimization is generally applicable to other conducting metal oxides.
    13. 13
      Wu, J. J. Appl. Phys. 2009, 106, 011101,  DOI: 10.1063/1.3155798
      13
      When group-III nitrides go infrared: New properties and perspectives
      Wu, Junqiao
      Journal of Applied Physics (2009), 106 (1), 011101/1-011101/28CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
      A review; wide-band-gap GaN and Ga-rich InGaN alloys, with energy gaps covering the blue and near-UV parts of the electromagnetic spectrum, are one group of the dominant materials for solid state lighting and lasing technologies and consequently, have been studied very well. Much less effort has been devoted to InN and In-rich InGaN alloys. A major breakthrough in 2002, stemming from much improved quality of InN films grown using mol. beam epitaxy, resulted in the bandgap of InN being revised from 1.9 eV to a much narrower value of 0.64 eV. This finding triggered a worldwide research thrust into the area of narrow-band-gap group-III nitrides. The low value of the InN bandgap provides a basis for a consistent description of the electronic structure of InGaN and InAlN alloys with all compns. It extends the fundamental bandgap of the group III-nitride alloy system over a wider spectral region, ranging from the near IR at ∼1.9 μm (0.64 eV for InN) to the UV at ∼0.36 μm (3.4 eV for GaN) or 0.2 μm (6.2 eV for AlN). The continuous range of bandgap energies now spans the near IR, raising the possibility of new applications for group-III nitrides. In this article we present a detailed review of the phys. properties of InN and related group III-nitride semiconductors. The electronic structure, carrier dynamics, optical transitions, defect physics, doping disparity, surface effects, and phonon structure will be discussed in the context of the InN bandgap re-evaluation. We will then describe the progress, perspectives, and challenges in the developments of new electronic and optoelectronic devices based on InGaN alloys. Advances in characterization and understanding of InN and InGaN nanostructures will also be reviewed in comparison to their thin film counterparts. (c) 2009 American Institute of Physics.
    14. 14
      King, P. D. C.; Veal, T. D.; Jefferson, P. H.; Hatfield, S. A.; Piper, L. F. J.; McConville, C. F.; Fuchs, F.; Furthmüller, J.; Bechstedt, F.; Lu, H.; Schaff, W. J. Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 77, 045316,  DOI: 10.1103/PhysRevB.77.045316
      There is no corresponding record for this reference.
    15. 15
      Terentjevs, A.; Catellani, A.; Cicero, G. Appl. Phys. Lett. 2010, 96, 171901,  DOI: 10.1063/1.3409224
      There is no corresponding record for this reference.
    16. 16
      Fan, G.; Wang, C.; Fang, J. Nano Today 2014, 9, 69,  DOI: 10.1016/j.nantod.2014.02.007
      16
      Solution-based synthesis of III-V quantum dots and their applications in gas sensing and bio-imaging
      Fan, Guangyin; Wang, Chenyu; Fang, Jiye
      Nano Today (2014), 9 (1), 69-84CODEN: NTAOCG; ISSN:1748-0132. (Elsevier Ltd.)
      A review. In recent years, the syntheses of III-V quantum dots have attracted extensive interests because of their remarkable quantum-confinement-effects, other attractive properties such as large exciton radius and potential applications in a no. of areas such as gas sensing and biol. probing. Some III-V members are low toxic and suitable to be used in bio-system with their excellent fluorescent characteristics. Although a soln.-phase prepn. of III-V quantum dots has become possible, the synthesis approach is still in its infancy and the quality of III-V products is inferior to those of II-VI and IV-VI quantum dots due to some difficulties such as lack of suitable precursors, high covalent characteristic, and difficult control of their nucleation and growth. The size, size distribution and crystallinity are strongly dependent on a specific reaction procedure and prepn. technique. It is also believed that the selection of suitable precursors and designing corresponding key reactions should hold the keys for a successful prodn. of the desired III-V quantum dots. This article focuses on the soln.-phase synthesis of In- and Ga-based III-V quantum dots, and these developments are presented through a classification of their chem. routes including metathesis, thermolysis, dehalosilylation and transmetalation with a discussion on their prepn. techniques such as one-pot heating-up and hot-injection. Furthermore, III-V quantum dots acted in gas sensing and bio-imaging applications are outlined as well. Eventually, an outlook of current challenges and promising direction for the development of III-V quantum dot synthesis is provided.
    17. 17
      Karan, N. S.; Chen, Y.; Liu, Z.; Beaulac, R. Chem. Mater. 2016, 28, 5601,  DOI: 10.1021/acs.chemmater.6b02417
      There is no corresponding record for this reference.
    18. 18
      Hsieh, J. C.; Yun, D. S.; Hu, E.; Belcher, A. M. J. Mater. Chem. 2010, 20, 1435,  DOI: 10.1039/b922196d
      There is no corresponding record for this reference.
    19. 19
      Choi, J.; Gillan, E. G. J. Mater. Chem. 2006, 16, 3774,  DOI: 10.1039/B608204A
      There is no corresponding record for this reference.
    20. 20
      Miura, A.; Takei, T.; Kumada, N. Cryst. Growth Des. 2012, 12, 4545,  DOI: 10.1021/cg3007266
      20
      Synthesis of Wurtzite-Type InN Crystals by Low-Temperature Nitridation of LiInO2 Using NaNH2 Flux
      Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro
      Crystal Growth & Design (2012), 12 (9), 4545-4547CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      Nitridation of oxides >500° is a conventional route for the synthesis of various oxynitrides and nitrides. However, this technique has the disadvantages of requiring a high temp. to break the strong metal and O bonds and of low use efficiency of N sources such as toxic NH3. Here, the authors show a simple low-temp. synthesis of InN nanocrystals via the nitridation of LiInO2 by NaNH2 flux at 240° in a Teflon-lined autoclave. The NaNH2 flux converted irregular-shaped LiInO2 powder to 50-300 nm InN nanocrystals with well-developed facets. The product crystd. in the hexagonal wurtzite structure with lattice parameters of a 3.545 and c 5.717 Å. Li in the starting oxide is essential for this low-temp. nitridation.
    21. 21
      Zhao, S.; Fathololoumi, S.; Bevan, K. H.; Liu, D. P.; Kibria, M. G.; Li, Q.; Wang, G. T.; Guo, H.; Mi, Z. Nano Lett. 2012, 12, 2877,  DOI: 10.1021/nl300476d
      There is no corresponding record for this reference.
    22. 22
      Tessarek, C.; Fladischer, S.; Dieker, C.; Sarau, G.; Hoffmann, B.; Bashouti, M.; Göbelt, M.; Heilmann, M.; Latzel, M.; Butzen, E.; Figge, S.; Gust, A.; Höflich, K.; Feichtner, T.; Büchele, M.; Schwarzburg, K.; Spiecker, E.; Christiansen, S. Nano Lett. 2016, 16, 3415,  DOI: 10.1021/acs.nanolett.5b03889
      22
      Self-Catalyzed Growth of Vertically Aligned InN Nanorods by Metal-Organic Vapor Phase Epitaxy
      Tessarek, C.; Fladischer, S.; Dieker, C.; Sarau, G.; Hoffmann, B.; Bashouti, M.; Goebelt, M.; Heilmann, M.; Latzel, M.; Butzen, E.; Figge, S.; Gust, A.; Hoeflich, K.; Feichtner, T.; Buechele, M.; Schwarzburg, K.; Spiecker, E.; Christiansen, S.
      Nano Letters (2016), 16 (6), 3415-3425CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      Vertically aligned hexagonal InN nanorods were grown mask-free by conventional OMVPE without any foreign catalyst. The In droplets on top of the nanorods indicate a self-catalytic vapor-liq.-solid growth mode. A systematic study on important growth parameters was carried out for the optimization of nanorod morphol. The nanorod N-polarity, induced by high temp. nitridation of the Al2O3 substrate, is necessary to achieve vertical growth. H2, usually inapplicable during InN growth due to formation of metallic In, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the Al2O3 surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temp. is similar. TEM, spatially resolved energy-dispersive x-ray spectroscopy, X-ray diffraction, XPS, and Raman spectroscopy were performed to analyze the structural properties. Spatially resolved cathodoluminescence studies are carried out to verify the optical activity of the InN nanorods.
    23. 23
      Kortshagen, U. J. Phys. D: Appl. Phys. 2009, 42, 113001,  DOI: 10.1088/0022-3727/42/11/113001
      23
      Nonthermal plasma synthesis of semiconductor nanocrystals
      Kortshagen, Uwe
      Journal of Physics D: Applied Physics (2009), 42 (11), 113001/1-113001/22CODEN: JPAPBE; ISSN:0022-3727. (Institute of Physics Publishing)
      A review, with 166 refs. Semiconductor nanocrystals have attracted considerable interest for a wide range of applications including light-emitting devices and displays, photovoltaic cells, nanoelectronic circuit elements, thermoelec. energy generation and luminescent markers in biomedicine. A particular advantage of semiconductor nanocrystals compared with bulk materials rests in their size-tunable optical, mech. and thermal properties. While nanocrystals of ionically bonded semiconductors can conveniently be synthesized with liq. phase chem., covalently bonded semiconductors require higher synthesis temps. Over the past decade, nonthermal plasmas have emerged as capable synthetic approaches for the covalently bonded semiconductor nanocrystals. Among the main advantages of nanocrystal synthesis in plasmas is the unipolar elec. charging of nanocrystals that helps avoid or reduce particle agglomeration and the selective heating of nanoparticles immersed in low-pressure plasmas. This paper discusses the important fundamental mechanisms of nanocrystal formation in plasmas, reviews the range of synthesis approaches reported in the literature and discusses some of the potential applications of plasma-synthesized semiconductor nanocrystals.
    24. 24
      Dixit, A.; Sudakar, J. S.; Thakur, K.; Padmanabhan, S.; Kumar, R.; Naik, R.; Naik, V. M.; Lawes, G. J. Appl. Phys. 2009, 105, 053104,  DOI: 10.1063/1.3088879
      24
      Strong plasmon absorption in InN thin films
      Dixit, A.; Sudakar, C.; Thakur, J. S.; Padmanabhan, K.; Kumar, Sanjiv; Naik, R.; Naik, V. M.; Lawes, G.
      Journal of Applied Physics (2009), 105 (5), 053104/1-053104/5CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
      The authors have fabricated InN thin films using radiofrequency magnetron sputtering from an In metal target. Optical and elec. measurements show that these as-grown films are n-type with carrier concns. ranging from 1020 to 1021 cm-3. This variation in carrier d. is produced by controlling the conditions during the deposition. The authors used Rutherford backscattering spectrometry to identify possible sources for n-type carriers. In addn. to strong direct bandgap optical absorption ranging from 1.4 to 2.0 eV, a large plasmon absorption peak in the IR region (0.45-0.8 eV) is also obsd. This tunable IR absorption suggests that these highly degenerate InN films could be used for a no. of applications, including optical filters and IR devices. (c) 2009 American Institute of Physics.
    25. 25
      Naik, V. M.; Naik, R.; Haddad, D. B.; Thakur, J. S.; Auner, G. W.; Lu, H.; Schaff, W. J. Appl. Phys. Lett. 2005, 86, 201913,  DOI: 10.1063/1.1935031
      There is no corresponding record for this reference.
    26. 26
      Palomaki, P. K. B.; Miller, E. M.; Neale, N. R. J. Am. Chem. Soc. 2013, 135, 14142,  DOI: 10.1021/ja404599g
      There is no corresponding record for this reference.
    27. 27
      Luther, J. M.; Jain, P. K.; Ewers, T.; Alivisatos, A. P. Nat. Mater. 2011, 10, 361,  DOI: 10.1038/nmat3004
      27
      Localized surface plasmon resonances arising from free carriers in doped quantum dots
      Luther, Joseph M.; Jain, Prashant K.; Ewers, Trevor; Alivisatos, A. Paul
      Nature Materials (2011), 10 (5), 361-366CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      Localized surface plasmon resonances (LSPRs) typically arise in nanostructures of noble metals resulting in enhanced and geometrically tunable absorption and scattering resonances. LSPRs are not limited to nanostructures of metals and can also be achieved in semiconductor nanocrystals with appreciable free carrier concns. Defined LSPRs arising from p-type carriers in vacancy-doped semiconductor quantum dots (QDs) are described. Achievement of LSPRs by free carrier doping of a semiconductor nanocrystal would allow active on-chip control of LSPR responses. Plasmonic sensing and manipulation of solid-state processes in single nanocrystals constitutes another interesting possibility. Doped semiconductor QDs allow realization of LSPRs and quantum-confined excitons within the same nanostructure, opening up the possibility of strong coupling of photonic and electronic modes, with implications for light harvesting, nonlinear optics, and quantum information processing.
    28. 28
      Klar, T.; Perner, M.; Grosse, S.; von Plessen, G.; Spirkl, W.; Feldmann, J. Phys. Rev. Lett. 1998, 80, 4249,  DOI: 10.1103/PhysRevLett.80.4249
      There is no corresponding record for this reference.
    29. 29
      Greenberg, B. L.; Ganguly, S.; Held, J. T.; Kramer, N. J.; Mkhoyan, K. A.; Aydil, E. S.; Kortshagen, E. S. Nano Lett. 2015, 15, 8162,  DOI: 10.1021/acs.nanolett.5b03600
      There is no corresponding record for this reference.
    30. 30
      Lounis, S. D.; Runnerstrom, E. L.; Bergerud, A.; Nordlund, D.; Milliron, D. J. J. Am. Chem. Soc. 2014, 136, 7110,  DOI: 10.1021/ja502541z
      30
      Influence of Dopant Distribution on the Plasmonic Properties of Indium Tin Oxide Nanocrystals
      Lounis, Sebastien D.; Runnerstrom, Evan L.; Bergerud, Amy; Nordlund, Dennis; Milliron, Delia J.
      Journal of the American Chemical Society (2014), 136 (19), 7110-7116CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Doped metal oxide nanocrystals represent an exciting frontier for colloidal synthesis of plasmonic materials, displaying unique optoelectronic properties and showing promise for a variety of applications. However, fundamental questions about the nature of doping in these materials remain. In this article, the strong influence of radial dopant distribution on the optoelectronic properties of colloidal indium tin oxide nanocrystals is reported. Comparing elemental depth-profiling by XPS with detailed modeling and simulation of the optical extinction of these nanocrystals using the Drude model for free electrons, a correlation between surface segregation of tin ions and the av. activation of dopants is obsd. A strong influence of surface segregation of tin on the line shape of the localized surface plasmon resonance (LSPR) is also reported. Samples with tin segregated near the surface show a sym. line shape that suggests weak or no damping of the plasmon by ionized impurities. It is suggested that segregation of tin near the surface facilitates compensation of the dopant ions by electronic defects and oxygen interstitials, thus reducing activation. A core-shell model is proposed to explain the obsd. differences in line shape. These results demonstrate the nuanced role of dopant distribution in detg. the optoelectronic properties of semiconductor nanocrystals and suggest that more detailed study of the distribution and structure of defects in plasmonic colloidal nanocrystals is warranted.
    31. 31
      Runnerstrom, E. L.; Bergerud, A.; Agrawal, A.; Johns, R. W.; Dahlman, C. J.; Singh, A.; Selbach, S. M.; Milliron, D. J. Nano Lett. 2016, 16, 3390,  DOI: 10.1021/acs.nanolett.6b01171
      There is no corresponding record for this reference.
    32. 32
      Ye, X.; Fei, J.; Diroll, B. T.; Paik, T.; Murray, C. B. J. Am. Chem. Soc. 2014, 136, 11680,  DOI: 10.1021/ja5039903
      There is no corresponding record for this reference.
    33. 33
      Wu, J.; Walukiewicz, W.; Shan, W.; Yu, K. M.; Ager, J. W.; Haller, E. E.; Lu, H.; Schaff, W. Phys. Rev. B: Condens. Matter Mater. Phys. 2002, 66, 201403,  DOI: 10.1103/PhysRevB.66.201403
      There is no corresponding record for this reference.
    34. 34
      Maruska, H. P.; Tietjen, J. J. Appl. Phys. Lett. 1969, 15, 327,  DOI: 10.1063/1.1652845
      There is no corresponding record for this reference.
    35. 35
      Ganchenkova, M. G.; Nieminen, R. M. Phys. Rev. Lett. 2006, 96, 196402,  DOI: 10.1103/PhysRevLett.96.196402
      There is no corresponding record for this reference.
    36. 36
      Piper, L. F. J.; Veal, T. D.; McConville, C. F.; Lu, H.; Schaff, W. J. Appl. Phys. Lett. 2006, 88, 252109,  DOI: 10.1063/1.2214156
      There is no corresponding record for this reference.
    37. 37
      Pilch, I.; Söderström, D.; Hasan, M. I.; Helmersson, U.; Brenning, N. Appl. Phys. Lett. 2013, 103, 193108,  DOI: 10.1063/1.4828883
      There is no corresponding record for this reference.
    38. 38
      Hasan, M. I.; Pilch, I.; Soderstrom, D.; Lundin, D.; Helmersson, U.; Brenning, N. Plasma Sources Sci. Technol. 2013, 22, 035006,  DOI: 10.1088/0963-0252/22/3/035006
      38
      Modeling the extraction of sputtered metal from high power impulse hollow cathode discharges
      Hasan, M. I.; Pilch, I.; Soederstroem, D.; Lundin, D.; Helmersson, U.; Brenning, N.
      Plasma Sources Science & Technology (2013), 22 (3), 035006/1-035006/12, 12 pp.CODEN: PSTEEU; ISSN:1361-6595. (IOP Publishing Ltd.)
      High power impulse hollow cathode sputtering is studied as a means to produce high fluxes of neutral and ionized sputtered metal species. A model is constructed for the understanding and optimization of such discharges. It relates input parameters such as the geometry of the cathode, the elec. pulse form and frequency, and the feed gas flow rate and pressure, to the prodn., ionization, temp. and extn. of the sputtered species. Examples of processes that can be quantified by the use of the model are the internal prodn. of sputtered metal and the degree of its ionization, the speed and efficiency of out-puffing from the hollow cathode assocd. with the pulses, and the gas back-flow into the hollow cathode between pulses. The use of the model is exemplified with a special case where the aim is the synthesis of nanoparticles in an expansion vol. that lies outside the hollow cathode itself. The goals are here a max. extn. efficiency, and a high degree of ionization of the sputtered metal. It is demonstrated that it is possible to reach a degree of ionization above 85%, and extn. efficiencies of 3% and 17% for the neutral and ionized sputtered components, resp.
    39. 39
      Rauch, C.; Tuomisto, F.; King, P. D. C.; Veal, T. D.; Lu, H.; Schaff, W. J. Appl. Phys. Lett. 2012, 101, 011903,  DOI: 10.1063/1.4732508
      There is no corresponding record for this reference.
    40. 40
      Look, D. C. Appl. Phys. Lett. 2002, 80, 258,  DOI: 10.1063/1.1432742
      There is no corresponding record for this reference.
    41. 41
      Duan, X. M.; Stampfl, C. Phys. Rev. B: Condens. Matter Mater. Phys. 2008, 77, 115207,  DOI: 10.1103/PhysRevB.77.115207
      There is no corresponding record for this reference.
    42. 42
      Jones, R. E.; Li, S. X.; Hsu, L.; Yu, K. M.; Walukiewicz, W.; Liliental-Weber, Z.; Ager, J. W.; Haller, E. E.; Lu, H.; Schaff, W. J. Phys. B 2006, 376-377, 436,  DOI: 10.1016/j.physb.2005.12.112
      42
      Native-defect-controlled n-type conductivity in InN
      Jones, R. E.; Li, S. X.; Hsu, L.; Yu, K. M.; Walukiewicz, W.; Liliental-Weber, Z.; Ager, J. W., III; Haller, E. E.; Lu, H.; Schaff, W. J.
      Physica B: Condensed Matter (Amsterdam, Netherlands) (2006), 376-377 (), 436-439CODEN: PHYBE3; ISSN:0921-4526. (Elsevier B.V.)
      High-energy particle irradn. was shown previously to be a method for n-type doping of InN. Here we irradiated InN with H+ and He+ particles to study the dependence of the electron mobility on electron concns. varying from mid-1018 to mid-1020 cm-3. We find that the electron mobility is limited by scattering from the ionized defects created by irradn., resulting in a strong correlation between mobility and electron concn. Furthermore, our calcns. suggest that the radiation-induced defects may be triply charged donors.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.nanolett.8b02260.

    • Details of the pulsed plasma process for growth of nanocrystals, FTIR spectra of nanocrystals with different sizes, calculations of the effective electron mass, and free electron concentration, UV–visible absorption measurements, and calculations of the nitrogen vacancies and electron mobility (PDF)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.