X-ray Imaging of Functional Three-Dimensional Nanostructures on Massive Substrates
- Diana A. GrishinaDiana A. GrishinaComplex Photonic Systems (COPS), MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The NetherlandsMore by Diana A. Grishina
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- Cornelis A. M. HarteveldCornelis A. M. HarteveldComplex Photonic Systems (COPS), MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The NetherlandsMore by Cornelis A. M. Harteveld
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- Alexandra PacureanuAlexandra PacureanuESRF-The European Synchrotron, CS40220, 38043 Grenoble, FranceMore by Alexandra Pacureanu
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- D. DevashishD. DevashishComplex Photonic Systems (COPS), MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The NetherlandsMore by D. Devashish
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- Ad LagendijkAd LagendijkComplex Photonic Systems (COPS), MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The NetherlandsMore by Ad Lagendijk
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- Peter Cloetens*Peter Cloetens*E-mail: [email protected]ESRF-The European Synchrotron, CS40220, 38043 Grenoble, FranceMore by Peter Cloetens
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- Willem L. Vos*Willem L. Vos*E-mail: [email protected]Complex Photonic Systems (COPS), MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The NetherlandsMore by Willem L. Vos
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Abstract
To investigate the performance of three-dimensional (3D) nanostructures, it is vital to study their internal structure with a methodology that keeps the device fully functional and ready for further integration. To this aim, we introduce here traceless X-ray tomography (TXT) that combines synchrotron X-ray holographic tomography with high X-ray photon energies (17 keV) in order to study nanostructures “as is” on massive silicon substrates. The combined strengths of TXT are a large total sample size to field-of-view ratio and a large penetration depth. We study exemplary 3D photonic band gap crystals made by CMOS-compatible means and obtain real space 3D density distributions with 55 nm spatial resolution. TXT identifies why nanostructures that look similar in electron microscopy have vastly different nanophotonic functionality: one “good” crystal with a broad photonic gap reveals 3D periodicity as designed; a second “bad” structure without a gap reveals a buried void, and a third “ugly” one without gap is shallow due to fabrication errors. Thus, TXT serves to nondestructively differentiate between the possible reasons of not finding the designed and expected performance and is therefore a powerful tool to critically assess 3D functional nanostructures.
Three-dimensional (3D) nanostructures are drawing a fast-growing attention for their advanced functionalities in nanophotonics, (1−6) photovoltaics, (7−9) and 3D integrated circuits and flash memories. (10−12) The functional properties of such nanostructures are fundamentally determined by their complex internal structure that consists of 3D arrangements of structural units such as spheres, rods, pores, or split rings. (13) Inevitably, any fabricated nanostructure differs from its initial design, systematically in the case of structural deformations, (14,15) and statistically in the case of size and positional disorder of the structural units. (16,17) Consequently, the observed functionality differs from the expected one.
It is therefore critical to assess the structure of a 3D nanomaterial and verify how well it matches the design. Ideally, such an inspection technique leaves no traces, keeping the nanostructure fully functional and ready for integration. To this end, we introduce here traceless X-ray tomography (TXT) as a methodology to the world of nanotechnology in order to nondestructively assess the functionality of the nanostructures. As a representative example, we study 3D periodic silicon photonic band gap crystals made by complementary metal-oxide semiconductor (CMOS)-compatible methods (see Figure 1A). (18,19) These nanostructures are powerful tools to control the propagation and the emission of light by their broad complete 3D photonic band gap (20,21) (see Figure 1B). We observe that TXT is ultimately limited only by the transmission loss of the X-ray signal while propagating through the nanostructure and its substrate. A transmission T > 10% is sufficient to preserve good photon statistics and avoid artifacts. Therefore, with the X-ray energy available with TXT (17 keV), massive sample–substrate combinations can be investigated. In the case of silicon, the maximum thickness is about 1.5 mm, sufficient for CMOS wafers. There are no limitations to the internal geometry of the nanostructures under study as periodic, random, or aperiodic structures can all be resolved.
Figure 1
Figure 1. Design of a 3D photonic crystal and its photonic functionality. (A) Cubic 3D inverse woodpile photonic crystals have a density distribution designed as two perpendicular 2D centered rectangular arrays (lattice parameters a, c; a/c = √2) of pores with radius r. Pores in the X-direction are aligned between pores in the Z-direction. (18) (B) Band diagram for an inverse woodpile crystal made from silicon reveals a broad 3D photonic band gap between a/λ = 0.60 and 0.75 (orange bar). In the experimentally probed Γ–X high-symmetry direction (panel 3× enlarged for clarity), the s-polarized stop gap (yellow) is broader than the p-polarized stop gap (black). (21)
Traditionally, in nanotechnology, a fabricated sample is inspected by scanning electron microscopy (SEM). (22) A major limitation of SEM, however, is that only the external surface is viewed, whereas the inner structure remains hidden. Indeed, Figure 2 shows three 3D photonic crystal nanostructures whose external surfaces look closely similar and closely match the design in Figure 1A (for sample description see the Methods section). However, the corresponding nanophotonic functionality shown in Figure 2 strongly differs: the crystal shown in panel A reveals a broad photonic gap as designed (panel B), whereas the other two structures reveal no gaps and instead a surprisingly constant reflectivity (panels D and F; for the setup, see the Methods section).
Figure 2
Figure 2. Scanning electron microscopy and nanophotonic functionality of three 3D photonic nanostructures. (A) SEM image of the external surface of a 3D inverse woodpile photonic crystal made from Si whose measured reflectivity spectrum (B) reveals a broad photonic gap in agreement with theory with input from TXT (yellow range). Horizontal black bars are estimated uncertainties in the TXT stop gap width. The blue range is the stop gap estimated from SEM data. (C) SEM image of a 3D photonic crystal whose reflectivity spectrum (D) reveals a constant low reflectivity with no gap. (E) SEM image of a 3D photonic crystal whose reflectivity spectrum (F) reveals a constant elevated reflectivity and no gap. In (A,C,E), the scale bar is 1 μm.
Functional verification, such as optical reflectivity, does not provide insights into the reasons why the performance of samples differs from design expectations. The reasons for different functional performance may be hidden in errors of the fabrication process, in errors in the design, or in errors of the functionality test itself. Therefore, to differentiate fabrication or design errors from performance test errors, it is necessary to know the actual 3D structure of the sample. In case the internal structure indeed matches the design while simultaneously the functionality differs from expectation, it is obvious that the sample should remain intact in order to perform further functionality studies, whence TXT.
To visualize 3D nanostructures, SEM is supplemented with micromachining or ion beam milling to cut away part of the structure. (22) Unfortunately, however, this approach is destructive, irreversible, and not in situ, hence packaged or buried structures will inevitably be broken. Whereas transmission electron microscopy (TEM) allows for high-resolution 3D imaging, the required sample thickness of less than 1 μm is insufficient for monolithic 3D photonic nanostructures. (23) X-ray techniques are well-suited due to their high penetration and high resolution. (24,25) Although small-angle X-ray scattering is employed to study 3D nanoparticle arrays, it naturally operates in reciprocal space, making it hard to characterize local nanosized features. (26,27) In contrast, X-ray tomography yields a real space 3D representation of the sample. (28) In traditional tomography, the contrast is provided by the sample absorption that is simply related to the brightness of the transmitted image called a radiograph. (29) As silicon and many materials that prevail in nanotechnology and in the CMOS industry absorb X-rays only weakly, however, advanced tomography methods are required.
Here, we obtain the relevant real space structural information directly from the optical phase change of the X-ray beam that propagates through the sample (for details, see the Methods section). The phase change is quantitatively retrieved from a set of radiographs taken at multiple sample-to-detector distances while rotating the sample. (30) Following a conventional tomographic reconstruction of the retrieved phase maps, the 3D electron density ρe(X,Y,Z) is obtained in real space as a stack of equally spaced 2D slices in the plane normal to the sample’s rotation axis. To achieve nanometer spatial resolution in a structure with millimeter thick substrates that do not need to be cut away, we employ X-ray holographic tomography with hard X-rays (31) (see the Methods section). Its main features are the X-ray beam that is focused and the sample that is placed at a small distance zs downstream from the focus to collect magnified Fresnel diffraction patterns on the detector.
Figure 3A shows a bird’s-eye view of the reconstructed sample volume of the 3D photonic crystal shown in Figure 2A,B. The YZ top face shows the surface of the X-directed pores, similar to the SEM surface in Figure 2A. The alignment of the pores determines the 3D crystal structure and is a crucial step in the nanofabrication. In practice, the alignment is controlled by the etch mask for each pore array and by the directionality of the etching processes. (32) In the XZ side face in Figure 3A, pores are running in the Z-direction, whereas in the XY front face, pores are running in the X-direction, matching the 3D design of the inverse woodpile structure (cf. Figure 1A), hence our nickname “the good”. In the XY front face, several pores appear as if they start “from nowhere” in the middle, which is simply due to their running slightly obliquely to the XY face (see Movie S2 and Movie S3), hence the top parts of the pores are not apparent.
Figure 3
Figure 3. 3D tomographic reconstructions of the three silicon nanostructures shown in the SEM images in Figure 2. (A,C,E) Bird’s-eye views of the reconstructed sample volumes, X-, Y-, and Z-axes are shown with each panel. (B,D,F) XZ cross sections taken midway through each sample; a 1 μm scale bar is shown in each slice. The common scale bar in panel (B) gives the electron density linearly interpolated between silicon (blue) and air (red). Movies S1, S2, and S3 present animations of the “good” sample shown in (A,B). Movie S4 presents cross sections of the “bad” sample shown in (C,D), and Movie S5 presents cross sections of the “ugly” sample shown in (E,F); see Supporting Information.
Figure 3B shows an XZ cross section midway through the 3D reconstructed volume that cuts through both arrays of pores and allows us to determine the maximum depths of both sets of pores (for YZ cross sections as a function of X, see Movie S2). The Z pores have a depth D = 6280 ± 20 nm and a radius r = 183 ± 10 nm, corresponding to a state-of-the-art depth-to-diameter aspect ratio of 17.15 ± 0.04, as expected from the deep reactive ion etching settings. (32,33) To date, the aspect ratio of pores deeply etched in silicon could only be assessed destructively and ex situ by SEM inspection of ion-milled slices or cleaved cross sections. (32,33) The deepest X pores have an even greater depth of 9460 ± 20 nm, corresponding to a high aspect ratio of 25.8 ± 0.1. This is an unequivocal observation that a second set of deep-etched pores runs even deeper than a first set. As the pore depth is a main limitation for a crystal’s size, 3D nanostructures are thus significantly larger than expected before. Clearly, TXT reveals buried structural features that are inaccessible to SEM or other nanocharacterization methods (atomic force microscopy or scanning transmission microscopy), as shown in Figure 3B, thus illustrating its power. Moreover, Figure 2B shows that the photonic gap estimated from TXT structural data agrees much better with the measured reflectivity stop band than the gap estimated from electron microscopy.
In addition to characterizing functional nanostructures, TXT allows one to identify several main deviations from the design that affect functionality. Figure 3C,D shows a bird’s-eye view and a cross section through a crystal whose external surface revealed usual crystalline features on a SEM image (cf. Figure 2C). The TXT reconstruction, however, reveals a buried internal void. The void is caused by stiction, (34) that is, the structural collapse of a nanostructure due to capillary action on the nanoscale due to the evaporation of a liquid. Here, the liquid was a suspension of colloidal quantum dots that was infiltrated in order to study spontaneous emission control (20) and subsequently the liquid spontaneously evaporated from the crystal. From TXT, we thus conclude that after the emission experiment, the crystal lost its functionality as a photonic band gap device, as is evident from the absence of a gap in reflectivity (see Figure 2D), and hence our nickname “the bad”.
Figure 3E,F shows a bird’s-eye view and a XZ cross section of a third sample whose external surface revealed usual periodic pore arrays in a SEM image (see Figure 2E). The tomographic reconstruction reveals a structure with pores that appear to be surprisingly shallow (about 70 nm in cross section) due to inadvertent erroneous settings during the etching process, hence our nickname “the ugly”. Thus, TXT allows us to conclude why this peculiar structure has no band gap functionality to begin with, as is apparent from the lack of gap in reflectivity (see Figure 2F), and the higher constant reflectivity (compared to Figure 2D) is obviously caused by the presence of bulk silicon.
One key feature of our TXT study is the use of X-rays with a much higher photon energy than before, (35−37) namely, 17 keV (compared to 6 or 8 keV). Therefore, the 1/e attenuation length for silicon is here 640 μm, that is, 9 to 20× greater than before, and sufficient to traverse wafer-thick silicon substrates that are ubiquitous in the CMOS industry. Therefore, we have been able to study nanostructures embedded in massive substrates with cross sections up to 1.07 × 106 μm2 “as is” without the need for irreversible sample preparation. In contrast, in recent papers, samples had to be destructively milled to a much smaller size (36) or had to be doped with heavy elements in order to obtain sufficient contrast. (35)
To characterize the TXT method, we define as a figure of merit F the ratio between the total linear sample size including substrate and the linear field of view (see Table 1). Due to the high photon energy and the holographic tomography method used here, we arrive at F = 86 (see Table 1), even without the need for extra data. In contrast, other interior or local tomography methods such as Fresnel zone plate or ptychography (38) have a limited F ≤ 3.3, while also requiring extra data taken with some empty beam next to the sample. In 2D ptychography of an integrated circuit, (39) the sample had to be thinned to 10 μm to allow sufficient X-ray transmission. On the contrary, a large F, as is demonstrated here, allows one to nondestructively study CMOS-compatible nanostructures “as is” and allows subsequent integration or fabrication steps.
Table 1. List of Samples Studied in This Paper with Their Nickname, Fabrication Method (First or Second Generation), Total Sample Cross Section Including Substrate As (μm)2, Figure of Merit 
(with Crystal Cross Section Acr = (12μm)2), and Pixel Volume in the Tomography Scans Vpix (nm3)a
(with Crystal Cross Section Acr = (12μm)2), and Pixel Volume in the Tomography Scans Vpix (nm3)a| name | fabrication method | As | F | Vpix |
|---|---|---|---|---|
| good | 1 | 1460(60) × 730(20) | 86(4) | 203 |
| bad | 1 | 480(20) × 410(30) | 37(3) | 203 |
| ugly | 2 | 500(50) × 530(20) | 43(5) | 103 |
a
Numbers between parentheses are estimated error margins.
Conclusion
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We have performed X-ray holographic tomography of 3D silicon photonic band gap crystals on massive substrates as a generic demonstration of traceless X-ray tomography of 3D nanomaterials. The method is truly traceless since we successfully recorded optical spectra even after the X-ray experiments. We obtain the 3D electron density and observe that the structural design is faithfully realized and leads to photonic functionality as expected. We uncover several buried structural deviations that help to identify the lack of functionality of faulty structures. We thus conclude that TXT is a powerful tool to assess the functionality of any complex 3D functional nanostructure with arbitrary short or long-range order, and allowing any subsequent integration or fabrication steps.
Methods
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3D Photonic Crystal Nanofabrication
The CMOS-compatible fabrication process of our 3D photonic band gap crystals was described previously. (32,40,41) In brief, in our first generation of photonic crystals, a hard mask is defined on a silicon wafer (thickness up to 0.73 mm) with a centered rectangular array of apertures, with a pore radius r/a = 0.245 that gives the broadest possible band gap. (15) Deep reactive ion etching of the first set of deep pores (in the Z-direction) results in a wafer with a large 2D array of deep pores. (32) Next, such a wafer is cleaved and polished and cut to a millimeter width to fit in the etching machine to perform the second etching step in the perpendicular direction. The second hard mask is carefully aligned with respect to the first array of pores (40) and defined in a 10 × 10 μm2 area on the side face of the wafer. By etching the second set of pores in the X-direction, the 3D nanostructure is obtained in the volume where both sets of pores overlap (see Figure 3 and the Movies S1–S3). Finally, the hard mask is removed. 3D photonic crystals shown in Figure 3A–D are fabricated in the above-mentioned way and are sitting on massive chips with large cross sections up to 0.73 × 1.46 = 1.07 mm2.
In our second generation of photonic crystals, the etch mask is deposited in a single step on both faces of a wafer edge, (41) followed by deep reactive ion etching of two perpendicular arrays of pores. As substrates, we employ Si beams that are chemically etched to cross sections of 0.5 × 0.5 mm2 to obtain exactly perpendicular crystal surfaces. The 3D photonic crystal shown in Figure 3E,F is an example of a second generation photonic crystal fabricated with the single-step etch mask. Although this particular sample was unsuccessful, this fabrication route has yielded many successful samples that have the intended 3D nanostructure, as confirmed by X-ray tomography (see Figure 4). Details of all samples are listed in Table 1.
Figure 4
Figure 4. Photographs of a typical sample studied by X-ray tomography. Top: Silicon beam with photonic crystal structures is mounted on a holder for the X-ray tomography scans. Center: Zoomed-in image of the top part of a Si beam, with a vertical row of 3D photonic crystal structures on the edge of the beam. In the defocused background, the edges of the beam-inclined surfaces are visible. Bottom: Further zoomed-in image reveals ten 3D photonic crystal structures that display a blueish iridescence due to their periodic surface structure. The edge of the beam appears as the vertical green line of scattered light.
Figure 4 shows photographs of a Si 3D nanostructured sample as it is studied in the X-ray tomography instrument “as is”, thus illustrating the power of TXT. The silicon-beam-shaped substrate measures 0.5 × 0.5 × 10 mm3 and is shown after fabrication in the MESA+ NanoLab (www.utwente.nl/mesaplus/nanolab) and mounted for X-ray holographic tomography scans at the ESRF. We emphasize that we do not mill a specific area out of the sample using, for instance, focused ion beams (FIB), as is used with other imaging techniques that require small sample volumes, such as X-ray ptychography, TEM, FIB-SEM, and so forth. We have successfully mounted all samples characterized by X-ray holographic tomography at ESRF in optical setups in Twente without further modifications and even in the same sample holder.
X-ray Holographic Tomography
Holographic tomography experiments were performed at the European Synchrotron Radiation Facility (ESRF), on the nanoimaging beamline ID16A-NI. (42) The hard X-ray beam with 17 keV photon energy propagates in the Z-direction and is focused with multilayer coated Kirkpatrick-Baez optics to a 23 × 37 nm2 focus. The sample is placed at a small distance zs downstream from the focus, and the detector is placed at a distance zd downstream from the sample, as shown in Figure 5.
Figure 5
Figure 5. (Top) Scheme of the synchrotron X-ray holotomography setup. The incident X-ray beam is focused using Kirkpatrick-Baez optics into a 23 × 37 nm2 focus. The sample is placed at a small distance zs downstream from the focus, and the detector is placed at a distance zd. Radiographs (one example shown) are recorded while rotating the sample by angle θ. (Bottom) Animation of tomography: data are recorded while rotating the sample (two orientations shown). From the recorded radiographs, the tomographic reconstruction is derived that is shown in the background.
The image recorded in the detector plane is an in-line Gabor hologram or Fresnel diffraction pattern. (43) Due to the focusing, the sample is illuminated with a spherical wave, unlike the plane-wave illumination in traditional tomography. According to the Fresnel scaling theorem, the spherical wave illumination gives rise to an effective propagation distance D and a magnification M given by (44,45)
Varying the focus-to-sample distance zs allows us to vary the magnification M of the diffraction patterns. It also strongly modifies the Fresnel diffraction pattern recorded on the detector through the effective propagation distance. For a phase periodic object, such as our photonic band gap crystals, the Talbot effect results in zero contrast for certain spatial frequencies at the characteristic Talbot distances. (46) To obtain nonzero contrast at all spatial frequencies, data are taken at four distances zs. The first distance was chosen to obtain a desired pixel size, either 10 or 20 nm (see Table 1). At each distance zs, Ni = 1500 images were recorded with 0.3 s exposure time while rotating the sample from θ = 0 to 180° around the Y-axis of the crystal (see Figure 2). After each set of rotations, additional radiographs at angles θ = 0 and 90° were collected that revealed that no irreversible changes occurred in the sample during the experiments. The number of projections Ni was chosen as a practical compromise between limited measurement time and sufficient spatial resolution, whereas the total sample size including substrate would require on the order of 105 projections in theory, our figure of merit F decrease this number by 2 orders of magnitude. For the tomographic scans, the axis of rotation was aligned to be a few micrometers deep inside the silicon.
(1)
X-ray Data Processing
The data processing is a two-step procedure consisting of a phase retrieval step followed by a tomographic reconstruction. The phase retrieval aims at retrieving the amplitude A(x,y) and phase ϕ(x,y) of the wave exiting the sample u0 = A(x,y)eiϕ(x,y) and that are given by
and
where λ is the X-ray wavelength. The amplitude and phase are thus the projection of, respectively, the absorption index β and the refractive index decrement δ that determine the complex refractive index for hard X-rays
Prior to phase retrieval, all sets of radiographs are scaled to the same magnification and mutually aligned. The mutual alignment of the radiographs at different distances is perturbed by the out-of-focus information on the thick samples. This problem is alleviated by refining this alignment iteratively using the calculated radiographs of the iterative phase retrieval step as a reference and aligning the experimental radiographs with respect to this reference.
(2)
(3)
(4)
We determine a first estimate of the amplitude and phase using the approach proposed by Paganin et al., (47) extended to multiple distances. We assume a homogeneous ratio δ/β = 174 for silicon at 17 keV photon energy. This first estimate provides a blurred version of the phase map. The map is recursively improved using 15 iterations of a nonlinear least-squares optimization. Due to the interior tomography problem, the boundary conditions are unknown in the phase retrieval step and the tomography reconstruction. The padding of the images—required in the propagation operators—and the filter step of the FBP tomography reconstruction are done as follows: The image at the largest distance (largest field of view) with an original size of 2048 (h) × 2048 (v) pixels is resampled to the highest magnification and 3216 × 3216 pixels. This image is padded to a size of 6144 × 4096 pixels by extending the boundary values with a smooth cosinus-type transition from one edge to the other. The images at higher magnification (and smaller field of view) are padded with the image data from the next lower magnification. The absence of any discontinuities in the padded images obtained in this way is effective to minimize the artifacts in the final reconstruction without the use of any supplementary data. The phase retrieval was carried out with ESRF in-house software using the GNU Octave programming environment (www.octave.org) and the public domain image analysis program ImageJ (see http://rsbweb.nih.gov/ij).
Second, a standard tomographic reconstruction (48) based on the filtered back-projection algorithm (49) and implemented in the ESRF software PyHST2 (50) allows us to obtain the distribution of the refractive index decrement δ(x, y, z). As the X-ray energy of 17 keV is far above any absorption edge of the materials under study, we obtain the electron density distribution from the well-known expression
with re is the classical electron radius. (51) The resulting structure was rendered with open-source software ParaView (see www.paraview.org).
(5)
Some phase projections are singular as the phase varies tremendously over a short distance when the X-rays are parallel to a sample face: 1.5 mm of Si introduces 216 rad phase shift at 17 keV. Therefore, about 10 projections near these singular angles (parallel to the X- or Z-directions) are omitted from the tomographic reconstruction.
In our nanostructures, the surrounding material introduces additional contrast that compounds the data interpretation, notably unpolished wafer backsurfaces with micron-high step sizes, sample corners, as well as surrounding deep 2D photonic crystal structures (some of these features are apparent in Movies S2 and S3). Fortunately, our method is sufficiently robust so that the structural features of the photonic crystals are clearly visible with sufficient spatial resolution.
Spatial Resolution
To investigate the spatial resolution, we inspected cross sections of reconstructed data within the large void of the “bad” sample as this structure presents several air–silicon interfaces. One line profile across an interface is shown as refractive index decrement in Figure 6. By modeling the data with a smooth curve and taking the derivative, we arrive at a full width at half-maximum resolution of 55 nm, corresponding to two-and-a-half 20 nm pixels.
Figure 6
Figure 6. Line profile across an air–Si interface in the “bad” sample shown as refractive index decrement (red circles). From the drawn curve, we derive a resolution of 55 nm.
Nanophotonic Experiments and Theory
To assess the basic functionality of the photonic crystals, we performed optical reflectivity to probe the designed photonic gaps. Optical reflectivity was measured using a home-built microscope setup that employs reflective optics and operates in the near-infrared range at wavelengths beyond 800 nm, see refs (52) and (53) and Supporting Information. Photonic band structures were calculated with the plane-wave expansion method, using the MIT photonic bands (MPB) code. (54) Silicon was modeled with a dielectric function ϵ = 12.1; see Supporting Information for further details.
Supporting Information
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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.9b05519.
Movie S1: Color rendering of the rotating “good” crystal (AVI)
Movie S2: Black and white cross sections of the “good” sample (AVI)
Movie S3: Black and white cross sections of the “good” sample (high resolution, emphasis on the surface) (AVI)
Movie S4: Black and white cross sections of the “bad” sample (AVI)
Movie S5: Black and white cross sections of the “ugly” sample (AVI)
CMOS compatibility, details of the reflectivity setup, details of the theory, features of the reconstructed crystals (PDF)
Terms & Conditions
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Author Information
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- Peter Cloetens - ESRF-The European Synchrotron, CS40220, 38043 Grenoble, France;
http://orcid.org/0000-0002-4129-9091;
- Willem L. Vos - Complex Photonic Systems (COPS), MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands;http://orcid.org/0000-0003-3066-859X;
- Alexandra Pacureanu - ESRF-The European Synchrotron, CS40220, 38043 Grenoble, France;http://orcid.org/0000-0003-2306-7040
Acknowledgments
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We thank Léon Woldering, Hannie van den Broek, Willem Tjerkstra, Simon Huisman, Rajesh Nair, Elena Pavlenko, Mehdi Aas, the MESA+ Nanolab and ESRF staff for help, and Arie den Boef (ASML), Jean-Michel Gérard (Grenoble), Hans Hilgenkamp, Detlef Lohse, Allard Mosk (Utrecht), Pepijn Pinkse, Julio da Silva, and Hasan Yilmaz (Yale) for fruitful discussions and support by the “Stirring of light!” program of the “Nederlandse Organisatie voor Wetenschappelijk Onderzoek” (NWO), the NWO-domain “Toegepaste en Technische Wetenschappen” (TTW) No. 11985, the Shell-NWO/FOM programme “Computational Sciences for Energy Research” (CSER), the MESA+ Institute for Nanotechnology (Applied Nanophotonics, ANP), and (thanks to to J.M.G.) and the Descartes-Huygens Prize of the French Academy of Sciences to W.L.V. We thank ESRF for granting beamtime through experiments HC-2520 and CH-5092.
References
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- 2Wijnhoven, J. E. G. J.; Vos, W. L. Preparation of Photonic Crystals Made of Air Spheres in Titania. Science 1998, 281, 802– 804, DOI: 10.1126/science.281.5378.802Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXlt1Snsbg%253D&md5=085b658c3f1fc44368a23c475e1d70bbPreparation of photonic crystals made of air spheres in TitaniaWijnhoven, Judith E. G. J.; Vos, Willem L.Science (Washington, D. C.) (1998), 281 (5378), 802-804CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Three-dimensional crystals of air spheres in TiO2 with radii between 120 and 1000 nm were made by filling the voids in artificial opals by pptn. from a liq.-phase chem. reaction and subsequently removing the original opal material by calcination. These macroporous materials are a new class of photonic band gap crystals for the optical spectrum. SEM, Raman spectroscopy, and optical microscopy confirm the quality of the samples, and optical reflectivity demonstrates that the crystals are strongly photonic and near that needed to exhibit band gap behavior.
- 3Noda, S.; Tomoda, K.; Yamamoto, N.; Chutinan, A. Full Three-Dimensional Photonic Bandgap Crystals at Near-Infrared Wavelengths. Science 2000, 289, 604– 606, DOI: 10.1126/science.289.5479.604Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXls1eksbs%253D&md5=7d304d9f168e5567181429b19780e065Full three-dimensional photonic bandgap crystals at near-infrared wavelengthsNoda, Susumu; Tomoda, Katsuhiro; Yamamoto, Noritsugu; Chutinan, AlongkarnScience (Washington, D. C.) (2000), 289 (5479), 604-606CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)An artificial crystal structure was fabricated exhibiting a full three-dimensional photonic bandgap effect at optical communication wavelengths. The photonic crystal was constructed by stacking 0.7-μm period semiconductor stripes with the accuracy of 30 nm by advanced wafer-fusion technique. A bandgap effect of >40 decibels (which corresponds to 99.99% reflection) was successfully achieved. The result encourages the authors to create an ultra-small optical integrated circuit including a three-dimensional photonic crystal waveguide with a sharp bend.
- 4Xia, Y.; Gates, B.; Li, Z. Y. Self-Assembly Approaches to Three-Dimensional Photonic Crystals. Adv. Mater. 2001, 13, 409– 413, DOI: 10.1002/1521-4095(200103)13:6<409::AID-ADMA409>3.0.CO;2-CGoogle Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXisFagtbc%253D&md5=0d60851cd46838c094e0157946a28327Self-assembly approaches to three-dimensional photonic crystalsXia, Younan; Gates, Byron; Li, Zhi-YuanAdvanced Materials (Weinheim, Germany) (2001), 13 (6), 409-413CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH)A review with 32 refs. of the historical development of photonic bandgap (PBG) materials is provided and the fabrication methods employed are discussed with emphasis on self-assembly processes. The factors influencing the generation of a complete bandgap, from both an exptl. and a calculational standpoint are then presented.
- 5Novotny, L.; Hecht, B. Principles of NanoOptics; Cambridge University Press: Cambridge, 2006.Google ScholarThere is no corresponding record for this reference.
- 6Tandaechanurat, A.; Ishida, S.; Guimard, D.; Nomura, M.; Iwamoto, S.; Arakawa, Y. Lasing Oscillation in a Three Dimensional Photonic Crystal Nanocavity with a Complete Bandgap. Nat. Photonics 2011, 5, 91– 94, DOI: 10.1038/nphoton.2010.286Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlOjtr8%253D&md5=78c51d0944118ac84e62b5d78cca11c3Lasing oscillation in a three-dimensional photonic crystal nanocavity with a complete bandgapTandaechanurat, Aniwat; Ishida, Satomi; Guimard, Denis; Nomura, Masahiro; Iwamoto, Satoshi; Arakawa, YasuhikoNature Photonics (2011), 5 (2), 91-94CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)Photonic crystals have been extensively used in the control and manipulation of photons in engineered electromagnetic environments provided by means of photonic bandgap effects. These effects are key to realizing future optoelectronic devices, including highly efficient lasers. To date, lasers based on photonic crystal cavities have been exclusively demonstrated in two-dimensional photonic crystal geometries. However, full confinement of photons and control of their interaction with materials can only be achieved with the use of three-dimensional photonic crystals with complete photonic bandgaps. We demonstrate, for the first time, the realization of lasing oscillation in a three-dimensional photonic crystal nanocavity. The laser is constructed by coupling a cavity mode exhibiting the highest quality factor yet achieved (∼38,500) with quantum dots. This achievement provides means for exploring the physics of light-matter interactions in a nanocavity-single quantum dot coupling system in which both photons and electrons are confined in three dimensions, as well as for realizing three-dimensional integrated photonic circuits.
- 7Bermel, P.; Luo, C.; Zeng, L.; Kimerling, L. C.; Joannopoulos, J. D. Improving Thin-Film Crystalline Silicon Solar Cell Efficiencies with Photonic Crystals. Opt. Express 2007, 15, 16986– 17000, DOI: 10.1364/OE.15.016986Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXitlersQ%253D%253D&md5=4b45a8c99636f1200fee501a68b5b9cfImproving thin-film crystalline silicon solar cell efficiencies with photonic crystalsBermel, Peter; Luo, Chiyan; Zeng, Lirong; Kimerling, Lionel C.; Joannopoulos, John D.Optics Express (2007), 15 (25), 16986-17000CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)Most photovoltaic (solar) cells are made from cryst. silicon (c-Si), which has an indirect band gap. This gives rise to weak absorption of one-third of usable solar photons. Therefore, improved light trapping schemes are needed, particularly for c-Si thin film solar cells. Here, a photonic crystal-based light-trapping approach is analyzed and compared to previous approaches. For a solar cell made of a 2 μm thin film of c-Si and a 6 bilayer distributed Bragg reflector (DBR) in the back, power generation can be enhanced by a relative amt. of 24.0% by adding a 1D grating, 26.3% by replacing the DBR with a six-period triangular photonic crystal made of air holes in silicon, 31.3% by a DBR plus 2D grating, and 26.5% by replacing it with an eight-period inverse opal photonic crystal.
- 8Atwater, H. A.; Polman, A. Plasmonics for Improved Photovoltaic Devices. Nat. Mater. 2010, 9, 205– 213, DOI: 10.1038/nmat2629Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXitFGltbg%253D&md5=6975cd4e62047de19d45766d775b1a9cPlasmonics for improved photovoltaic devicesAtwater, Harry A.; Polman, AlbertNature Materials (2010), 9 (3), 205-213CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)In this review, we survey recent advances at the intersection of plasmonics and photovoltaics and offer an outlook on the future of solar cells based on these principles. The emerging field of plasmonics has yielded methods for guiding and localizing light at the nanoscale, well below the scale of the wavelength of light in free space. Now plasmonics researchers are turning their attention to photovoltaics, where design approaches based on plasmonics can be used to improve absorption in photovoltaic devices, permitting a considerable redn. in the phys. thickness of solar photovoltaic absorber layers, and yielding new options for solar-cell design.
- 9Battaglia, C.; Hsu, C.; Soderstrom, K.; Escarre, J.; Haug, F.; Charriere, M.; Boccard, M.; Despeisse, M.; Alexander, D. T. L.; Cantoni, M.; Cui, Y.; Ballif, C. Light Trapping in Solar Cells: Can Periodic Beat Random?. ACS Nano 2012, 6, 2790– 2797, DOI: 10.1021/nn300287jGoogle Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XjtVGhurY%253D&md5=04bfc0aa161568a8ef95e6875759365eLight Trapping in Solar Cells: Can Periodic Beat Random?Battaglia, Corsin; Hsu, Ching-Mei; Soderstrom, Karin; Escarre, Jordi; Haug, Franz-Josef; Charriere, Mathieu; Boccard, Mathieu; Despeisse, Matthieu; Alexander, Duncan T. L.; Cantoni, Marco; Cui, Yi; Ballif, ChristopheACS Nano (2012), 6 (3), 2790-2797CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Theory predicts that periodic photonic nanostructures should outperform their random counterparts in trapping light in solar cells. However, the current certified world-record conversion efficiency for amorphous silicon thin-film solar cells, which strongly rely on light trapping, was achieved on the random pyramidal morphol. of transparent zinc oxide electrodes. Based on insights from waveguide theory, we develop tailored periodic arrays are developed of nanocavities on glass fabricated by nanosphere lithog., which enable a cell with a remarkable short-circuit c.d. of 17.1 mA/cm2 and a high initial efficiency of 10.9%. A direct comparison with a cell deposited on the random pyramidal morphol. of state-of-the-art zinc oxide electrodes, replicated onto glass using nanoimprint lithog., demonstrates unambiguously that periodic structures rival random textures.
- 10Anthony, S. IBM Creates First Cheap, Commercially Viable, Electronic Photonic Integrated Chip, 2012; http://www.extremetech.com/computing/142881-ibm-creates-firstcheap-commercially-viable-siliconnanophotonic-chip (accessed Dec 10 2016).Google ScholarThere is no corresponding record for this reference.
- 11Samsung V-NAND (vertical-NAND) Technology (white Paper), 2014; https://www.samsung.com/us/business/oem-solutions/pdfs/VNAND_technology_WP.pdf (accessed Dec 10 2016).Google ScholarThere is no corresponding record for this reference.
- 12Crippa, L.; Micheloni, R. In 3D Flash Memories; Micheloni, R., Ed.; Springer: Dordrecht, 2016; pp 85– 127.Google ScholarThere is no corresponding record for this reference.
- 13Soukoulis, C. M.; Wegener, M. Past Achievements and Future Challenges in the Development of Three-Dimensional Photonic Metamaterials. Nat. Photonics 2011, 5, 523– 530, DOI: 10.1038/nphoton.2011.154Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtV2qurjL&md5=43a91aada4a819f2b5d593f2c8d1e783Past achievements and future challenges in the development of three-dimensional photonic metamaterialsSoukoulis, Costas M.; Wegener, MartinNature Photonics (2011), 5 (9), 523-530CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)A review. Photonic metamaterials are man-made structures composed of tailored micro- or nanostructured metallodielec. subwavelength building blocks. This deceptively simple yet powerful concept allows the realization of many new and unusual optical properties, such as magnetism at optical frequencies, neg. refractive index, large pos. refractive index, zero reflection through impedance matching, perfect absorption, giant CD and enhanced nonlinear optical properties. Possible applications of metamaterials include ultrahigh-resoln. imaging systems, compact polarization optics and cloaking devices. This Review describes recent progress in the fabrication of three-dimensional metamaterial structures and discusses some of the remaining challenges.
- 14Fan, S. H.; Villeneuve, P. R.; Joannopoulos, J. D. Theoretical Investigation of Fabrication-Related Disorder on the Properties of Photonic Crystals. J. Appl. Phys. 1995, 78, 1415– 1418, DOI: 10.1063/1.360298Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXntVOqsr8%253D&md5=e5547d9fc5baeb8dd9160c2c309c604aTheoretical investigation of fabrication-related disorder on the properties of photonic crystalsFan, Shanhui; Villeneuve, Pierre R.; Joannopoulos, J. D.Journal of Applied Physics (1995), 78 (3), 1415-18CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)How various deviations in perfect photonic band gaps was studied theor. The emphasis is on detg. the effects of misalignment of basic structural elements and overall surface roughness, because of their general fabrication relevance. As an example, calcns. on a newly proposed three-dimensional photonic crystal were performed. The size of the gap is tolerant to significant amts. of deviation from the perfect structure.
- 15Woldering, L. A.; Mosk, A. P.; Tjerkstra, R. W.; Vos, W. L. The Influence of Fabrication Deviations on the Photonic Band Gap of Three-Dimensional Inverse Woodpile Nanostructures. J. Appl. Phys. 2009, 105, 093108 DOI: 10.1063/1.3103777Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXlslGmt7g%253D&md5=40f549e6b72fcd15d29ce6520ed1fa47The influence of fabrication deviations on the photonic band gap of three-dimensional inverse woodpile nanostructuresWoldering, Leon A.; Mosk, Allard P.; Tjerkstra, R. Willem; Vos, Willem L.Journal of Applied Physics (2009), 105 (9), 093108/1-093108/10CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The effects of unintended deviations from ideal inverse woodpile photonic crystals on the photonic band gap are discussed. Such deviations occur during the nanofabrication of the crystal. By computational analyses it is shown that the band gap of this type of crystal is robust to most types of deviations that relate to the radii, position, and angular alignment of the pores. However, the photonic band gap is very sensitive to tapering of the pores, i.e., conically shaped pores instead of cylindrical pores. To obtain three-dimensional inverse woodpile photonic crystals with a large vol., our work shows that with modern fabrication performances, redn. in tapering contributes most significantly to a high photonic strength. (c) 2009 American Institute of Physics.
- 16Hughes, S.; Ramunno, L.; Young, J. F.; Sipe, J. E. Extrinsic Optical Scattering Loss in Photonic Crystal Waveguides: Role of Fabrication Disorder and Photon Group Velocity. Phys. Rev. Lett. 2005, 94, 033903 DOI: 10.1103/PhysRevLett.94.033903Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXpt1SgsQ%253D%253D&md5=e244ab114e8b1c47d996e0983a1157a2Extrinsic Optical Scattering Loss in Photonic Crystal Waveguides: Role of Fabrication Disorder and Photon Group VelocityHughes, S.; Ramunno, L.; Young, Jeff F.; Sipe, J. E.Physical Review Letters (2005), 94 (3), 033903/1-033903/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Formulas are presented that provide clear phys. insight into the phenomenon of extrinsic optical scattering loss in photonic crystal waveguides due to random fabrication imperfections such as surface roughness and disorder. Using a photon Green-function-tensor formalism, the authors derive explicit expressions for the backscattered and total transmission losses. Detailed calcns. for planar photonic crystals yield extrinsic loss values in overall agreement with exptl. measurements, including the full dispersion characteristics. The authors also report that loss in photonic crystal waveguides scales inversely with group velocity, at least, thereby raising serious questions about future low-loss applications based on operating frequencies that approach the photonic band edge.
- 17Koenderink, A. F.; Lagendijk, A.; Vos, W. L. Optical Extinction Due to Intrinsic Structural Variations of Photonic Crystals. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 153102, DOI: 10.1103/PhysRevB.72.153102Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1WgsLvF&md5=09cbe65712cdb4f569ce73231af72e1aOptical extinction due to intrinsic structural variations of photonic crystalsKoenderink, A. Femius; Lagendijk, Ad; Vos, Willem L.Physical Review B: Condensed Matter and Materials Physics (2005), 72 (15), 153102/1-153102/4CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)Unavoidable variations in size and position of the building blocks of photonic crystals cause light scattering and extinction of coherent beams. We present a model for both two- and three-dimensional photonic crystals that relates the extinction length to the magnitude of the variations. The predicted lengths agree well with our expts. on high-quality opals and inverse opals, and with literature data analyzed by us. As a result, control over photons is limited to distances up to 50 lattice parameters (∼15 μm) in state-of-the-art structures, thereby impeding applications that require large photonic crystals, such as proposed optical integrated circuits. Conversely, scattering in photonic crystals may lead to different physics such as Anderson localization and nonclassical diffusion.
- 18Ho, K. M.; Chan, C. T.; Soukoulis, C. M.; Biswas, R.; Sigalas, M. Photonic Band Gaps in Three Dimensions: New Layer-by-Layer Periodic Structures. Solid State Commun. 1994, 89, 413– 416, DOI: 10.1016/0038-1098(94)90202-XGoogle Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2cXitlSjtLc%253D&md5=e9644238a3c9bc239f0937d21d71a1a0Photonic band gaps in three dimensions: new layer-by-layer periodic structuresHo, K. M.; Chan, C. T.; Soukoulis, C. M.; Biswas, R.; Sigalas, M.Solid State Communications (1994), 89 (5), 413-16CODEN: SSCOA4; ISSN:0038-1098.A new 3-dimensional (3D) periodic dielec. structure constructed with layers of dielec. rods of circular, elliptical, or rectangular shape is introduced. This new structure possesses a full photonic band gap of appreciable frequency width. At midgap, an attenuation of 21 dB per unit cell is obtained. This gap remains open for refractive indexes n ≥ 1.9. Also, this new 3-dimensional layer structure potentially has the addnl. advantage that it can be easily fabricated using conventional microfabrication techniques on the scale of optical wavelengths.
- 19Maldovan, M.; Thomas, E. L. Diamond Structured Photonic Crystals. Nat. Mater. 2004, 3, 593– 600, DOI: 10.1038/nmat1201Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXntlGitbc%253D&md5=00313acbdaf468c9a7623c46502e08f3Diamond-structured photonic crystalsMaldovan, Martin; Thomas, Edwin L.Nature Materials (2004), 3 (9), 593-600CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)A review. Certain periodic dielec. structures can prohibit the propagation of light for all directions within a frequency range. These photonic crystals allow researchers to modify the interaction between electromagnetic fields and dielec. media from radio to optical wavelengths. Their technol. potential, such as the inhibition of spontaneous emission, enhancement of semiconductor lasers, and integration and miniaturization of optical components, makes the search for an easy-to-craft photonic crystal with a large bandgap a major field of study. This progress article surveys a collection of robust complete 3-dimensional dielec. photonic-bandgap structures for the visible and near-IR regimes based on the diamond morphol. together with their specific fabrication techniques. The basic origin of the complete photonic bandgap for the champion diamond morphol. is described in terms of dielec. modulations along principal directions. Progress in 3-dimensional interference lithog. for fabrication of near-champion diamond-based structures is also discussed.
- 20Leistikow, M. D.; Mosk, A. P.; Yeganegi, E.; Huisman, S. R.; Lagendijk, A.; Vos, W. L. Inhibited Spontaneous Emission of Quantum Dots Observed in a 3D Photonic Band Gap. Phys. Rev. Lett. 2011, 107, 193903, DOI: 10.1103/PhysRevLett.107.193903Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsV2ktbzL&md5=c6904314bd48aa11f64d00aad728b26cInhibited Spontaneous Emission of Quantum Dots Observed in a 3D Photonic Band GapLeistikow, M. D.; Mosk, A. P.; Yeganegi, E.; Huisman, S. R.; Lagendijk, A.; Vos, W. L.Physical Review Letters (2011), 107 (19), 193903/1-193903/5CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)We present time-resolved emission expts. of semiconductor quantum dots in silicon 3D inverse-woodpile photonic band gap crystals. A systematic study is made of crystals with a range of pore radii to tune the band gap relative to the emission frequency. The decay rates averaged over all dipole orientations are inhibited by a factor of 10 in the photonic band gap and enhanced up to 2× outside the gap, in agreement with theory. We discuss the effects of spatial inhomogeneity, nonradiative decay, and transition dipole orientations on the obsd. inhibition in the band gap.
- 21Devashish, D.; Hasan, S. B.; van der Vegt, J. J. W.; Vos, W. L. Reflectivity Calculated for a Three-Dimensional Silicon Photonic Band Gap Crystal with Finite Support. Phys. Rev. B: Condens. Matter Mater. Phys. 2017, 95, 155141, DOI: 10.1103/PhysRevB.95.155141Google ScholarThere is no corresponding record for this reference.
- 22Goldstein, J.; Newbury, D. E.; Joy, D. C.; Lyman, C. E.; Echlin, P.; Lifshim, E.; Sawyer, L.; Michael, J. R. Scanning Electron Microscopy and X-Ray Microanalysis; Springer: New York, 2003.Google ScholarThere is no corresponding record for this reference.
- 23Jacobsen, C.; Medewaldt, R.; Williams, S. In X-ray Microscopy and Spectromicroscopy; Thieme, J., Schmahl, G., Rudolph, D., Umbach, E., Eds.; Springer: New York, 1998; pp 197– 206.Google ScholarThere is no corresponding record for this reference.
- 24Misra, S.; Liu, N.; Nelson, J.; Hong, S. S.; Cui, Y.; Toney, M. In Situ X-Ray Diffraction Studies of (De)Lithiation Mechanism in Silicon Nanowire Anodes. ACS Nano 2012, 6, 5465– 5473, DOI: 10.1021/nn301339gGoogle Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XmsFGjtbs%253D&md5=b314a19360d8a47b8d600fc1b1fcd04eIn Situ X-ray Diffraction Studies of (De)lithiation Mechanism in Silicon Nanowire AnodesMisra, Sumohan; Liu, Nian; Nelson, Johanna; Hong, Seung Sae; Cui, Yi; Toney, Michael F.ACS Nano (2012), 6 (6), 5465-5473CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Silicon is a promising anode material for Li-ion batteries due to its high theor. specific capacity. From previous work, silicon nanowires are known to undergo amorphorization during lithiation, and no cryst. Li-Si product has been obsd. In this work, we use an x-ray transparent battery cell to perform in situ synchrotron x-ray diffraction on silicon nanowires in real time during electrochem. cycling. At deep lithiation voltages the known metastable Li15Si4 phase forms, and we show that avoiding the formation of this phase, by modifying the silicon nanowire growth temp., improves the cycling performance of silicon nanowire anodes. Our results provide insight on the (de)lithiation mechanism and a correlation between phase evolution and electrochem. performance for silicon nanowire anodes.
- 25Stankevič, T.; Hilner, E.; Seiboth, F.; Ciechonski, R.; Vescovi, G.; Kryliouk, O.; Johansson, U.; Samuelson, L.; Wellenreuther, G.; Falkenberg, G.; Feidenhansl, R.; Mikkelsen, A. Fast Strain Mapping of Nanowire Light-Emitting Diodes Using Nanofocused X-Ray Beams. ACS Nano 2015, 9, 6978– 6984, DOI: 10.1021/acsnano.5b01291Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVKisbvM&md5=22b3626eda6347a1c6ed226e0650d7a1Fast Strain Mapping of Nanowire Light-Emitting Diodes Using Nanofocused X-ray BeamsStankevic, Tomas; Hilner, Emelie; Seiboth, Frank; Ciechonski, Rafal; Vescovi, Giuliano; Kryliouk, Olga; Johansson, Ulf; Samuelson, Lars; Wellenreuther, Gerd; Falkenberg, Gerald; Feidenhans'l, Robert; Mikkelsen, AndersACS Nano (2015), 9 (7), 6978-6984CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)X-ray nanobeams are unique nondestructive probes that allow direct measurements of the nanoscale strain distribution and compn. inside the micrometer thick layered structures that are found in most electronic device architectures. However, the method is usually extremely time-consuming, and as a result, data sets are often constrained to a few or even single objects. Here we demonstrate that by special design of a nanofocused X-ray beam diffraction expt. we can (in a single 2D scan with no sample rotation) measure the individual strain and compn. profiles of many structures in an array of upright standing nanowires. We make use of the observation that in the generic nanowire device configuration, which is found in high-speed transistors, solar cells, and light-emitting diodes, each wire exhibits very small degrees of random tilts and twists toward the substrate. Although the tilt and twist are very small, they give a new contrast mechanism between different wires. In the present case, we image complex nanowires for nanoLED fabrication and compare to theor. simulations, demonstrating that this fast method is suitable for real nanostructured devices.
- 26Vos, W. L.; Megens, M.; van Kats, C. M.; Bösecke, P. X-Ray Diffraction of Photonic Colloidal Single Crystals. Langmuir 1997, 13, 6004– 6008, DOI: 10.1021/la970423nGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmvVals7w%253D&md5=f78655afedb2c7e0caa821b6956006f1X-ray Diffraction of Photonic Colloidal Single CrystalsVos, Willem L.; Megens, Mischa; van Kats, Carlos M.; Boesecke, PeterLangmuir (1997), 13 (23), 6004-6008CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The authors have resolved a great no. of Bragg peaks of photonic colloidal single crystals by synchrotron small angle x-ray scattering (SAXS). Charge-stabilized colloids form fcc. crystals at all densities up to ∼60 vol.%. The colloidal particles are highly ordered on their lattice sites, which confirms that these self-organizing materials are suitable building blocks for optical photonic matter. Synchrotron SAXS with two-dimensional detection is a powerful tool to study systems with length scales comparable to optical wavelengths.
- 27Shabalin, A. G.; Meijer, J.-M.; Dronyak, R.; Yefanov, O. M.; Singer, A.; Kurta, R. P.; Lorenz, U.; Gorobtsov, O. Y.; Dzhigaev, D.; Kalbfleisch, S.; Gulden, J.; Zozulya, A. V.; Sprung, M.; Petukhov, A. V.; Vartanyants, I. A. Revealing Three-Dimensional Structure of an Individual Colloidal Crystal Grain by Coherent X-Ray Diffractive Imaging. Phys. Rev. Lett. 2016, 117, 138002, DOI: 10.1103/PhysRevLett.117.138002Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Gku7c%253D&md5=f1987dcca3b5b338e6717c75fdcffbdbRevealing three-dimensional structure of an individual colloidal crystal grain by coherent x-ray diffractive imagingShabalin, A. G.; Meijer, J.-M.; Dronyak, R.; Yefanov, O. M.; Singer, A.; Kurta, R. P.; Lorenz, U.; Gorobtsov, O. Y.; Dzhigaev, D.; Kalbfleisch, S.; Gulden, J.; Zozulya, A. V.; Sprung, M.; Petukhov, A. V.; Vartanyants, I. A.Physical Review Letters (2016), 117 (13), 138002/1-138002/6CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)We present results of a coherent x-ray diffractive imaging expt. performed on a single colloidal crystal grain. The full three-dimensional (3D) reciprocal space map measured by an azimuthal rotational scan contained several orders of Bragg reflections together with the coherent interference signal between them. Applying the iterative phase retrieval approach, the 3D structure of the crystal grain was reconstructed and positions of individual colloidal particles were resolved. As a result, an exact stacking sequence of hcp. layers including planar and linear defects were identified.
- 28Sakdinawat, A.; Attwood, D. Nanoscale X-Ray Imaging. Nat. Photonics 2010, 4, 840– 848, DOI: 10.1038/nphoton.2010.267Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsVygs7jE&md5=e5a54791ee55916a851ac499006a5bd0Nanoscale X-ray imagingSakdinawat, Anne; Attwood, DavidNature Photonics (2010), 4 (12), 840-848CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)Recent years have seen significant progress in the field of soft- and hard-X-ray microscopy, both tech., through developments in source, optics and imaging methodologies, and also scientifically, through a wide range of applications. While an ever-growing community is pursuing the extensive applications of today's available X-ray tools, other groups are investigating improvements in techniques, including new optics, higher spatial resolns., brighter compact sources and shorter-duration X-ray pulses. This Review covers recent work in the development of direct image-forming X-ray microscopy techniques and the relevant applications, including three-dimensional biol. tomog., dynamical processes in magnetic nanostructures, chem. speciation studies, industrial applications related to solar cells and batteries, and studies of archaeol. materials and historical works of art.
- 29Pollak, B. Experiences With Planography. Dis. Chest 1953, 24, 663– 669, DOI: 10.1378/chest.24.6.663Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADyaG2c%252FivVCrsQ%253D%253D&md5=7e4823b3842e60f9ed9e7d9fc9346ddeExperiences with planographyPOLLAK BDiseases of the chest (1953), 24 (6), 663-9 ISSN:0096-0217.There is no expanded citation for this reference.
- 30Cloetens, P.; Ludwig, W.; Baruchel, J.; van Dyck, D.; van Landuyt, J.; Guigay, J. P.; Schlenker, M. Holotomography: Quantative Phase Tomography with Micrometer Resolution Using Hard Synchrotron Radiation X Rays. Appl. Phys. Lett. 1999, 75, 2912– 2914, DOI: 10.1063/1.125225Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXmvFChurY%253D&md5=45b3236fa08a8f33e3de858d766ea383Holotomography. Quantitative phase tomography with micrometer resolution using hard synchrotron radiation x raysCloetens, P.; Ludwig, W.; Baruchel, J.; Van Dyck, D.; Van Landuyt, J.; Guigay, J. P.; Schlenker, M.Applied Physics Letters (1999), 75 (19), 2912-2914CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Because the refractive index for hard x rays is slightly different from unity, the optical phase of a beam is affected by transmission through an object. Phase images can be obtained with extreme instrumental simplicity by simple propagation provided the beam is coherent. But, unlike absorption, the phase is not simply related to image brightness. A holog. reconstruction procedure combining images taken at different distances from the specimen was developed. It results in quant. phase mapping and, through assocn. with 3D reconstruction, in holotomog., the complete 3D mapping of the d. in a sample. This tool in the characterization of materials at the micrometer scale is uniquely suited to samples with low absorption contrast and radiation-sensitive systems.
- 31Mokso, R.; Cloetens, P.; Maire, E.; Ludwig, W.; Buffière, J.-Y. Nanoscale Zoom Tomography with Hard X-Rays Using Kirkpatrick-Baez Optics. Appl. Phys. Lett. 2007, 90, 144104, DOI: 10.1063/1.2719653Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXksV2jt70%253D&md5=4ac904d5c4c03a0c25c39b6dfe8f57f0Nanoscale zoom tomography with hard x-rays using Kirkpatrick-Baez opticsMokso, R.; Cloetens, P.; Maire, E.; Ludwig, W.; Buffiere, J.-Y.Applied Physics Letters (2007), 90 (14), 144104/1-144104/3CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)To overcome the limitations in terms of spatial resoln. and field of view of existing tomog. techniques, a hard x-ray projection microscope is realized based on the sub-100-nm focus produced by Kirkpatrick-Baez optics. The sample is set at a small distance downstream of the focus and Fresnel diffraction patterns with variable magnification are recorded on a medium-resoln. detector. While the approach requires a specific phase retrieval procedure and correction for mirror imperfections, it allows zooming nondestructively into bulky samples. Quant. 3-dimensional nanoscale microscopy is demonstrated on an Al alloy in local tomog. mode.
- 32van den Broek, J. M.; Woldering, L. A.; Tjerkstra, R. W.; Segerink, F. B.; Setija, I. D.; Vos, W. L. Inverse-Woodpile Photonic Band Gap Crystals with a Cubic Diamond-Like Structure Made from Single Crystalline Silicon. Adv. Funct. Mater. 2012, 22, 25– 31, DOI: 10.1002/adfm.201101101Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXht1equ7vF&md5=0817d8cb2b0f4829f37fd7458ca448e4Inverse-Woodpile Photonic Band Gap Crystals with a Cubic Diamond-like Structure Made from Single-Crystalline Siliconvan den Broek, J. M.; Woldering, L. A.; Tjerkstra, R. W.; Segerink, F. B.; Setija, I. D.; Vos, W. L.Advanced Functional Materials (2012), 22 (1), 25-31CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)Three dimensional photonic band gap crystals with a cubic diamond-like symmetry are fabricated. These so-called inverse-woodpile nanostructures consist of 2 perpendicular sets of pores in single-crystal Si wafers and are made by complementary metal oxide-semiconductor (CMOS)-compatible methods. Both sets of pores have high aspect ratios and are made by deep reactive-ion etching. The mask for the 1st set of pores is defined in Cr by deep UV scan-and-step technol. The mask for the 2nd set of pores is patterned using an ion beam and carefully placed at an angle of 90° with an alignment precision of better than 30 nm. Crystals are made with pore radii between 135-186 nm with lattice parameters a 686. and c 488. nm such that a/c = √2; hence the structure is cubic. The crystals are characterized using SEM and x-ray diffraction. By milling away slices of crystal, the pores are analyzed in detail in both directions regarding depth, radius, tapering, shape, and alignment. Using optical reflectivity the crystals have broad reflectivity peaks in the near-IR frequency range, which includes the telecommunication range. The strong reflectivity confirms the high quality of the photonic crystals. Also the width of the reflectivity peaks agrees well with gaps in calcd. photonic band structures.
- 33Wu, B.; Kumar, A.; Pamarthy, S. High Aspect Ratio Silicon Etch: A Review. J. Appl. Phys. 2010, 108, 051101 DOI: 10.1063/1.3474652Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtFekt7bI&md5=876ed35bb39b9e9fd300e4c3466d53a2High aspect ratio silicon etch: A reviewWu, Banqiu; Kumar, Ajay; Pamarthy, SharmaJournal of Applied Physics (2010), 108 (5), 051101/1-051101/20CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)A review. High aspect ratio (HAR) Si etch is reviewed, including commonly used terms, history, main applications, different technol. methods, crit. challenges, and main theories of the technologies. Chronol., HAR Si etch was conducted using wet etch in soln., reactive ion etch (RIE) in low d. plasma, single-step etch at cryogenic conditions in inductively coupled plasma (ICP) combined with RIE, time-multiplexed deep silicon etch in ICP-RIE configuration reactor, and single-step etch in high d. plasma at room or near room temp. Key specifications are HAR, high etch rate, good trench sidewall profile with smooth surface, low aspect ratio dependent etch, and low etch loading effects. Until now, temp-multiplexed etch process is a popular industrial practice but the intrinsic scalloped profile of a time-multiplexed etch process, resulting from alternating between passivation and etch, poses a challenge. Previously, HAR Si etch was an application assocd. primarily with microelectromech. systems. In recent years, through-Si-via (TSV) etch applications for 3-dimensional integrated circuit stacking technol. has spurred research and development of this enabling technol. This potential large scale application requires HAR etch with high and stable throughput, controllable profile and surface properties, and low costs. (c) 2010 American Institute of Physics.
- 34Roman, B.; Bico, J. Elasto-Capillarity: Deforming an Elastic Structure with a Liquid Droplet. J. Phys.: Condens. Matter 2010, 22, 493101, DOI: 10.1088/0953-8984/22/49/493101Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXjs1ahuw%253D%253D&md5=0225b6f8365e3cb1cfd6b4a58563f692Elasto-capillarity: deforming an elastic structure with a liquid dropletRoman, B.; Bico, J.Journal of Physics: Condensed Matter (2010), 22 (49), 493101/1-493101/16CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)A review. Although negligible at macroscopic scales, capillary forces become dominant as the sub-millimetric scales of micro-electro-mech. systems (MEMS) are considered. We review various situations, not limited to micro-technologies, where capillary forces are able to deform elastic structures. In particular, we define the different length scales that are relevant for 'elasto-capillary' problems. We focus on the case of slender structures (lamellae, rods and sheets) and describe the size of a bundle of wet hair, the condition for a flexible rod to pierce a liq. interface or the fate of a liq. droplet deposited on a flexible thin sheet. These results can be generalized to similar situations involving adhesion or fracture energy, which widens the scope of possible applications from biol. systems, to stiction issues in micro-fabrication processes, the manufg. of 3D microstructures or the formation of blisters in thin film coatings.
- 35Chen, Y. C.; Geddes, J. B.; Yin, L.; Wiltzius, P.; Braun, P. V. X-Ray Computed Tomography of Holographically Fabricated Three-Dimensional Photonic Crystals. Adv. Mater. 2012, 24, 2863– 2868, DOI: 10.1002/adma.201200411Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XmtlWktLo%253D&md5=2eecfde5a01b3cb4c07d631153351196X-Ray Computed Tomography of Holographically Fabricated Three-Dimensional Photonic CrystalsChen, Ying-Chieh; Geddes, Joseph B.; Yin, Leilei; Wiltzius, Pierre; Braun, Paul V.Advanced Materials (Weinheim, Germany) (2012), 24 (21), 2863-2868CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)The authors have demonstrated real-space 3D imaging of holog. defined photonic crystals (PC) via x-ray computed tomog. (CT) on a HfO2 in-filled SU-8-based PC sample. To the best of the authors knowledge, this study is the first use of x-ray CT to characterize the morphol. of a 3D PC. The reconstructed structure used for calcn. of reflectance spectra agreed with the measured spectra. The geometry of the reconstructed structure was compared with the previously reported modeled structure. The two structures exhibited 85 % geometric agreement between them, and the observable differences explained the relatively higher reflectance spectra displayed by the reconstructed structure over the modeled structure. By using x-ray tomog. to measure the fabricated PC, it is now possible to investigate the deformation process from an as made PC through processing. Several factors were considered to account for this deformation and may include crosslink d. variations and material loss during development. This improved understanding of the correlation between the interference pattern and final fabricated PC structure can facilitate the design of PCs, including those contg. engineered embedded defects, for photonic applications.
- 36Holler, M.; Guizar-Sicairos, M.; Tsai, E. H. R.; Dinapoli, R.; Müller, E.; Bunk, O.; Raabe, J.; Aeppli, G. High Resolution Non-Destructive Three Dimensional Imaging of Integrated Circuits. Nature (London, U. K.) 2017, 543, 402– 406, DOI: 10.1038/nature21698Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlslensLs%253D&md5=ee2d3b0da96c9d8b5ce45caf33fe1a25High-resolution non-destructive three-dimensional imaging of integrated circuitsHoller, Mirko; Guizar-Sicairos, Manuel; Tsai, Esther H. R.; Dinapoli, Roberto; Muller, Elisabeth; Bunk, Oliver; Raabe, Jorg; Aeppli, GabrielNature (London, United Kingdom) (2017), 543 (7645), 402-406CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Modern nanoelectronics has advanced to a point at which it is impossible to image entire devices and their interconnections non-destructively because of their small feature sizes and the complex three-dimensional structures resulting from their integration on a chip. This metrol. gap implies a lack of direct feedback between design and manufg. processes, and hampers quality control during prodn., shipment and use. Here we demonstrate that X-ray ptychog.-a high-resoln. coherent diffractive imaging technique-can create three-dimensional images of integrated circuits of known and unknown designs with a lateral resoln. in all directions down to 14.6 nm. We obtained detailed device geometries and corresponding elemental maps, and show how the devices are integrated with each other to form the chip. Our expts. represent a major advance in chip inspection and reverse engineering over the traditional destructive electron microscopy and ion milling techniques. Foreseeable developments in X-ray sources, optics and detectors, as well as adoption of an instrument geometry optimized for planar rather than cylindrical samples, could lead to a thousand-fold increase in efficiency, with concomitant redns. in scan times and voxel sizes.
- 37Furlan, K. P.; Larsson, E.; Diaz, A.; Holler, M.; Krekeler, T.; Ritter, M.; Petrov, A. Y.; Eich, M.; Blick, R.; Schneider, G. A.; Greving, I.; Zierold, R.; Janen, R. Photonic Materials for HighTemperature Applications: Synthesis and Characterization by X-Ray Ptychographic Tomography. Appl. Mater. Today 2018, 13, 359– 369, DOI: 10.1016/j.apmt.2018.10.002Google ScholarThere is no corresponding record for this reference.
- 38da Silva, J. C.; Guizar-Sicairos, M.; Holler, M.; Diaz, A.; van Bokhoven, J. A.; Bunk, O.; Menzel, A. Quantitative Region-Of-Interest Tomography Using Variable Field of View. Opt. Express 2018, 26, 16752– 16768, DOI: 10.1364/OE.26.016752Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitlyjsLvP&md5=7e47b7c3a184c51b987a8c916f2458aeQuantitative region-of-interest tomography using variable field of viewDa Silva, J. C.; Guizar-Sicairos, M.; Holler, M.; Diaz, A.; Van Bokhoven, J. A.; Bunk, O.; Menzel, A.Optics Express (2018), 26 (13), 16752-16768CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)In X-ray computed tomog., the task of imaging only a local region of interest (ROI) inside a larger sample is very important. However, without a priori information, this ROI cannot be exactly reconstructed using only the image data limited to the ROI. We propose here an approach of region-of-interest tomog., which reconstructs a ROI within an object from projections of different fields of view acquired on a specific angular sampling scheme in the same tomog. expt. We present a stable procedure that not only yields high-quality images of the ROI but keeps as well the quant. contrast on the reconstructed images. In addn., we analyze the min. no. of projections required for ROI tomog. from the point of view of the band region of the Radon transform, which confirms this no. must be estd. based on the size of the entire object and not only on the size of the ROI.
- 39Guizar-Sicairos, M.; Johnson, I.; Diaz, A.; Holler, M.; Karvinen, P.; Stadler, H. C.; Dinapoli, R.; Bunk, O.; Menzel, A. HighThroughput Ptychography Using Eiger: Scanning X-Ray Nano-Imaging of Extended Regions. Opt. Express 2014, 22, 14859– 14870, DOI: 10.1364/OE.22.014859Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2cfot1GhtA%253D%253D&md5=f70b5ac076f9a1ad08dd5d145ed48aadHigh-throughput ptychography using Eiger: scanning X-ray nano-imaging of extended regionsGuizar-Sicairos Manuel; Johnson Ian; Diaz Ana; Holler Mirko; Karvinen Petri; Stadler Hans-Christian; Dinapoli Roberto; Bunk Oliver; Menzel AndreasOptics express (2014), 22 (12), 14859-70 ISSN:.The smaller pixel size and high frame rate of next-generation photon counting pixel detectors opens new opportunities for the application of X-ray coherent diffractive imaging (CDI). In this manuscript we demonstrate fast image acquisition for ptychography using an Eiger detector. We achieve above 25,000 resolution elements per second, or an effective dwell time of 40 μs per resolution element, when imaging a 500 μm × 290 μm region of an integrated electronic circuit with 41 nm resolution. We further present the application of a scheme of sharing information between image parts that allows the field of view to exceed the range of the piezoelectric scanning system and requirements on the stability of the illumination to be relaxed.
- 40Tjerkstra, R. W.; Woldering, L. A.; van den Broek, J. M.; Roozeboom, F.; Setija, I. D.; Vos, W. L. Method to Pattern Etch Masks in Two Inclined Planes for Three Dimensional Nano- and Microfabricationy. J. Vac. Sci. Technol., B: Nanotechnol. Microelectron.: Mater., Process., Meas., Phenom. 2011, 29, 061604 DOI: 10.1116/1.3662000Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xht1aqurs%253D&md5=a1afacd4116397991fb37b020010a00fMethod to pattern etch masks in two inclined planes for three-dimensional nano- and microfabricationTjerkstra, R. Willem; Woldering, Leon A.; van den Broek, Johanna M.; Roozeboom, Fred; Setija, Irwan D.; Vos, Willem L.Journal of Vacuum Science & Technology, B: Nanotechnology & Microelectronics: Materials, Processing, Measurement, & Phenomena (2011), 29 (6), 061604/1-061604/8CODEN: JVSTCN ISSN:. (American Institute of Physics)The authors present a method to pattern etch masks for arbitrary nano- and microstructures on different, inclined planes of a sample. Our method allows std. CMOS fabrication techniques to be used in different inclined planes; thus yielding three-dimensional structures with a network topol. The method involves processing of the sample in a first plane, followed by mounting the prepd. sample in a specially designed silicon holder wafer such that the second, inclined plane is exposed to continued processing. As a proof of principle we demonstrate the fabrication of a patterned chromium etch mask for three-dimensional photonic crystals in silicon. The etch mask is made on the 90° inclined plane of a silicon sample that already contains high aspect ratio nanopores. The etch mask is carefully aligned with respect to these pores, with a high translational accuracy of <30 nm along the y-axis and a high rotational accuracy of 0.71° around the z-axis of the crystal. Such high alignment precisions are crucial for nanophotonics and for sub-micrometer applications in general. Although we limit ourselves to processing on two planes of a sample, it is in principle possible to repeat the presented method on more planes. The authors foresee potential applications of this technique in, e.g., microfluidics, photonics, and three-dimensional silicon electronics. (c) 2011 American Institute of Physics.
- 41Grishina, D. A.; Harteveld, C. A. M.; Woldering, L. A.; Vos, W. L. Method to Make a Single-Step Etch Mask for 3D Monolithic Nanostructures. Nanotechnology 2015, 26, 505302, DOI: 10.1088/0957-4484/26/50/505302Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtVOlu7vP&md5=6fa2f6a94c1fb320e73ef1a5d0e0c85aMethod for making a single-step etch mask for 3D monolithic nanostructuresGrishina, D. A.; Harteveld, C. A. M.; Woldering, L. A.; Vos, W. L.Nanotechnology (2015), 26 (50), 505302/1-505302/10CODEN: NNOTER; ISSN:1361-6528. (IOP Publishing Ltd.)Current nanostructure fabrication by etching is usually limited to planar structures as they are defined by a planar mask. The realization of three-dimensional (3D) nanostructures by etching requires technologies beyond planar masks. We present a method for fabricating a 3D mask that allows one to etch three-dimensional monolithic nanostructures using only CMOS-compatible processes. The mask is written in a hard-mask layer that is deposited on two adjacent inclined surfaces of a Si wafer. By projecting in a single step two different 2D patterns within one 3D mask on the two inclined surfaces, the mutual alignment between the patterns is ensured. Thereby after the mask pattern is defined, the etching of deep pores in two oblique directions yields a three-dimensional structure in Si. As a proof of concept we demonstrate 3D mask fabrication for three-dimensional diamond-like photonic band gap crystals in silicon. The fabricated crystals reveal a broad stop gap in optical reflectivity measurements. We propose how 3D nanostructures with five different Bravais lattices can be realized, namely cubic, tetragonal, orthorhombic, monoclinic and hexagonal, and demonstrate a mask for a 3D hexagonal crystal. We also demonstrate the mask for a diamond-structure crystal with a 3D array of cavities. In general, the 2D patterns on the different surfaces can be completely independently structured and still be in perfect mutual alignment. Indeed, we observe an alignment accuracy of better than 3.0 nm between the 2D mask patterns on the inclined surfaces, which permits one to etch welldefined monolithic 3D nanostructures.
- 42Cesar da Silva, J.; Pacureanu, A.; Yang, Y.; Bohic, S.; Morawe, C.; Barrett, R.; Cloetens, P. Efficient Concentration of High-Energy XRays for Diffraction-Limited Imaging Resolution. Optica 2017, 4, 492– 495, DOI: 10.1364/OPTICA.4.000492Google ScholarThere is no corresponding record for this reference.
- 43Gabor, D. A New Microscopic Principle. Nature (London, U. K.) 1948, 161, 777– 778, DOI: 10.1038/161777a0Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADyaH1c%252FgsVSgug%253D%253D&md5=66f5aa921ddb675bc2696abb775f2166A new microscopic principleGABOR DNature (1948), 161 (4098), 777 ISSN:0028-0836.There is no expanded citation for this reference.
- 44Pogany, D.; Gao, A.; Wilkins, S. W. Contrast and Resolution in Imaging with a Microfocus X-Ray Source. Rev. Sci. Instrum. 1997, 68, 2774– 2782, DOI: 10.1063/1.1148194Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXkslWnu7Y%253D&md5=1f39904b428a60172cf3ae94838fe3f7Contrast and resolution in imaging with a microfocus x-ray sourcePogany, A.; Gao, D.; Wilkins, S. W.Review of Scientific Instruments (1997), 68 (7), 2774-2782CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)A simple general treatment of x-ray image formation by Fresnel diffraction is presented; the image can alternatively be considered as an in-line hologram. Particular consideration is given to phase-contrast microscopy and imaging using hard x-rays. The theory makes use of the optical transfer function in a similar way to that used in the theory of electron microscope imaging. Resoln. and contrast are the criteria used to specify the visibility of an image. Resoln. in turn depends primarily on the spatial coherence of the illumination, with chromatic coherence of lesser importance. Thus broadband microfocus sources can give useful phase-contrast images. Both plane-and spherical-wave conditions are explicitly considered as limiting cases appropriate to macroscopic imaging and microscopy, resp., while intermediate cases may also be of practical interest. Some results are presented for x-ray images showing phase contrast.
- 45Paganin, D. Coherent X-ray Optics; Oxford University Press: Oxford, 2006.Google ScholarThere is no corresponding record for this reference.
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- 47Paganin, D.; Mayo, S. C.; Gureyev, T. E.; Miller, P. R.; Wilkins, S. W. Simultaneous Phase and Amplitude Extraction from a Single Defocused Image of a Homogeneous Object. J. Microsc. 2002, 206, 33– 40, DOI: 10.1046/j.1365-2818.2002.01010.xGoogle Scholar47https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BD383mtVWmtg%253D%253D&md5=87e8b3e1d788a6446f03db60666ff48dSimultaneous phase and amplitude extraction from a single defocused image of a homogeneous objectPaganin D; Mayo S C; Gureyev T E; Miller P R; Wilkins S WJournal of microscopy (2002), 206 (Pt 1), 33-40 ISSN:0022-2720.We demonstrate simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object. Subject to the assumptions explicitly stated in the derivation, the algorithm solves the twin-image problem of in-line holography and is capable of analysing data obtained using X-ray microscopy, electron microscopy, neutron microscopy or visible-light microscopy, especially as they relate to defocus and point projection methods. Our simple, robust, non-iterative and computationally efficient method is applied to data obtained using an X-ray phase contrast ultramicroscope.
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- 50Mirone, A.; Brun, E.; Gouillart, E.; Tafforeau, P.; Kieffer, J. The pyhst2 Hybrid Distributed Code for High Speed Tomographic Reconstruction with Iterative Reconstruction and a Priori Knowledge Capabilities. Nucl. Instrum. Methods Phys. Res., Sect. B 2014, 324, 41– 48, DOI: 10.1016/j.nimb.2013.09.030Google Scholar50https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhslSktrw%253D&md5=1fbdebda8990e395da588222496a6ad2The PyHST2 hybrid distributed code for high speed tomographic reconstruction with iterative reconstruction and a priori knowledge capabilitiesMirone, Alessandro; Brun, Emmanuel; Gouillart, Emmanuelle; Tafforeau, Paul; Kieffer, JeromeNuclear Instruments & Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms (2014), 324 (), 41-48CODEN: NIMBEU; ISSN:0168-583X. (Elsevier B.V.)We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomog. This code has been engineered to sustain the high data flow typical of the 3rd generation synchrotron facilities (10 terabytes per expt.) by adopting a distributed and pipelined architecture. The code implements, beside a default filtered backprojection reconstruction, iterative reconstruction techniques with a priori knowledge. These latter are used to improve the reconstruction quality or in order to reduce the required data vol. or the deposited dose to the sample and reach a given quality goal. The implemented a priori knowledge techniques are based on the total variation penalization and a new recently found convex functional which is based on overlapping patches. We give details of the different methods and discuss how they are implemented in the PyHST2 code, which is distributed under free license. We provide methods for estg., in the absence of ground-truth data, the optimal parameters values for a priori techniques.
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- 52Huisman, S. R.; Nair, R.; Woldering, L. A.; Leistikow, M. D.; Mosk, A. P.; Vos, W. L. Signature of a Three-Dimensional Photonic Band Bap Observed on Silicon Inverse Woodpile Photonic Crystals. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 83, 205313, DOI: 10.1103/PhysRevB.83.205313Google Scholar52https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXotVyktLc%253D&md5=40248dab9957cbdfc59c8f8fa93e590fSignature of a three-dimensional photonic band gap observed on silicon inverse woodpile photonic crystalsHuisman, Simon R.; Nair, Rajesh V.; Woldering, Leon A.; Leistikow, Merel D.; Mosk, Allard P.; Vos, Willem L.Physical Review B: Condensed Matter and Materials Physics (2011), 83 (20), 205313/1-205313/7CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)The authors have studied the reflectivity of CMOS-compatible 3-dimensional Si inverse woodpile photonic crystals at near-IR frequencies. Polarization-resolved reflectivity spectra were obtained from 2 orthogonal crystal surfaces using an objective with a high numerical aperture. The spectra reveal broad peaks with max. reflectivity of 67% that are independent of the spatial position on the crystals. The spectrally overlapping reflectivity peaks for all directions and polarizations form the signature of a broad photonic band gap with a relative bandwidth up to 16%. This signature is supported with stop gaps in plane-wave band-structure calcns. and with the frequency region of the expected band gap.
- 53Adhikary, M.; Uppu, R.; Harteveld, C. A. M.; Grishina, D. A.; Vos, W. L. Experimental Probe of a Complete 3D Photonic Band Gap. arXiv.org 1909.01899 2019.Google ScholarThere is no corresponding record for this reference.
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Abstract
Figure 1
Figure 1. Design of a 3D photonic crystal and its photonic functionality. (A) Cubic 3D inverse woodpile photonic crystals have a density distribution designed as two perpendicular 2D centered rectangular arrays (lattice parameters a, c; a/c = √2) of pores with radius r. Pores in the X-direction are aligned between pores in the Z-direction. (18) (B) Band diagram for an inverse woodpile crystal made from silicon reveals a broad 3D photonic band gap between a/λ = 0.60 and 0.75 (orange bar). In the experimentally probed Γ–X high-symmetry direction (panel 3× enlarged for clarity), the s-polarized stop gap (yellow) is broader than the p-polarized stop gap (black). (21)
Figure 2
Figure 2. Scanning electron microscopy and nanophotonic functionality of three 3D photonic nanostructures. (A) SEM image of the external surface of a 3D inverse woodpile photonic crystal made from Si whose measured reflectivity spectrum (B) reveals a broad photonic gap in agreement with theory with input from TXT (yellow range). Horizontal black bars are estimated uncertainties in the TXT stop gap width. The blue range is the stop gap estimated from SEM data. (C) SEM image of a 3D photonic crystal whose reflectivity spectrum (D) reveals a constant low reflectivity with no gap. (E) SEM image of a 3D photonic crystal whose reflectivity spectrum (F) reveals a constant elevated reflectivity and no gap. In (A,C,E), the scale bar is 1 μm.
Figure 3
Figure 3. 3D tomographic reconstructions of the three silicon nanostructures shown in the SEM images in Figure 2. (A,C,E) Bird’s-eye views of the reconstructed sample volumes, X-, Y-, and Z-axes are shown with each panel. (B,D,F) XZ cross sections taken midway through each sample; a 1 μm scale bar is shown in each slice. The common scale bar in panel (B) gives the electron density linearly interpolated between silicon (blue) and air (red). Movies S1, S2, and S3 present animations of the “good” sample shown in (A,B). Movie S4 presents cross sections of the “bad” sample shown in (C,D), and Movie S5 presents cross sections of the “ugly” sample shown in (E,F); see Supporting Information.
Figure 4
Figure 4. Photographs of a typical sample studied by X-ray tomography. Top: Silicon beam with photonic crystal structures is mounted on a holder for the X-ray tomography scans. Center: Zoomed-in image of the top part of a Si beam, with a vertical row of 3D photonic crystal structures on the edge of the beam. In the defocused background, the edges of the beam-inclined surfaces are visible. Bottom: Further zoomed-in image reveals ten 3D photonic crystal structures that display a blueish iridescence due to their periodic surface structure. The edge of the beam appears as the vertical green line of scattered light.
Figure 5
Figure 5. (Top) Scheme of the synchrotron X-ray holotomography setup. The incident X-ray beam is focused using Kirkpatrick-Baez optics into a 23 × 37 nm2 focus. The sample is placed at a small distance zs downstream from the focus, and the detector is placed at a distance zd. Radiographs (one example shown) are recorded while rotating the sample by angle θ. (Bottom) Animation of tomography: data are recorded while rotating the sample (two orientations shown). From the recorded radiographs, the tomographic reconstruction is derived that is shown in the background.
Figure 6
Figure 6. Line profile across an air–Si interface in the “bad” sample shown as refractive index decrement (red circles). From the drawn curve, we derive a resolution of 55 nm.
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- 15Woldering, L. A.; Mosk, A. P.; Tjerkstra, R. W.; Vos, W. L. The Influence of Fabrication Deviations on the Photonic Band Gap of Three-Dimensional Inverse Woodpile Nanostructures. J. Appl. Phys. 2009, 105, 093108 DOI: 10.1063/1.3103777Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXlslGmt7g%253D&md5=40f549e6b72fcd15d29ce6520ed1fa47The influence of fabrication deviations on the photonic band gap of three-dimensional inverse woodpile nanostructuresWoldering, Leon A.; Mosk, Allard P.; Tjerkstra, R. Willem; Vos, Willem L.Journal of Applied Physics (2009), 105 (9), 093108/1-093108/10CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)The effects of unintended deviations from ideal inverse woodpile photonic crystals on the photonic band gap are discussed. Such deviations occur during the nanofabrication of the crystal. By computational analyses it is shown that the band gap of this type of crystal is robust to most types of deviations that relate to the radii, position, and angular alignment of the pores. However, the photonic band gap is very sensitive to tapering of the pores, i.e., conically shaped pores instead of cylindrical pores. To obtain three-dimensional inverse woodpile photonic crystals with a large vol., our work shows that with modern fabrication performances, redn. in tapering contributes most significantly to a high photonic strength. (c) 2009 American Institute of Physics.
- 16Hughes, S.; Ramunno, L.; Young, J. F.; Sipe, J. E. Extrinsic Optical Scattering Loss in Photonic Crystal Waveguides: Role of Fabrication Disorder and Photon Group Velocity. Phys. Rev. Lett. 2005, 94, 033903 DOI: 10.1103/PhysRevLett.94.033903Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXpt1SgsQ%253D%253D&md5=e244ab114e8b1c47d996e0983a1157a2Extrinsic Optical Scattering Loss in Photonic Crystal Waveguides: Role of Fabrication Disorder and Photon Group VelocityHughes, S.; Ramunno, L.; Young, Jeff F.; Sipe, J. E.Physical Review Letters (2005), 94 (3), 033903/1-033903/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Formulas are presented that provide clear phys. insight into the phenomenon of extrinsic optical scattering loss in photonic crystal waveguides due to random fabrication imperfections such as surface roughness and disorder. Using a photon Green-function-tensor formalism, the authors derive explicit expressions for the backscattered and total transmission losses. Detailed calcns. for planar photonic crystals yield extrinsic loss values in overall agreement with exptl. measurements, including the full dispersion characteristics. The authors also report that loss in photonic crystal waveguides scales inversely with group velocity, at least, thereby raising serious questions about future low-loss applications based on operating frequencies that approach the photonic band edge.
- 17Koenderink, A. F.; Lagendijk, A.; Vos, W. L. Optical Extinction Due to Intrinsic Structural Variations of Photonic Crystals. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 153102, DOI: 10.1103/PhysRevB.72.153102Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXht1WgsLvF&md5=09cbe65712cdb4f569ce73231af72e1aOptical extinction due to intrinsic structural variations of photonic crystalsKoenderink, A. Femius; Lagendijk, Ad; Vos, Willem L.Physical Review B: Condensed Matter and Materials Physics (2005), 72 (15), 153102/1-153102/4CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)Unavoidable variations in size and position of the building blocks of photonic crystals cause light scattering and extinction of coherent beams. We present a model for both two- and three-dimensional photonic crystals that relates the extinction length to the magnitude of the variations. The predicted lengths agree well with our expts. on high-quality opals and inverse opals, and with literature data analyzed by us. As a result, control over photons is limited to distances up to 50 lattice parameters (∼15 μm) in state-of-the-art structures, thereby impeding applications that require large photonic crystals, such as proposed optical integrated circuits. Conversely, scattering in photonic crystals may lead to different physics such as Anderson localization and nonclassical diffusion.
- 18Ho, K. M.; Chan, C. T.; Soukoulis, C. M.; Biswas, R.; Sigalas, M. Photonic Band Gaps in Three Dimensions: New Layer-by-Layer Periodic Structures. Solid State Commun. 1994, 89, 413– 416, DOI: 10.1016/0038-1098(94)90202-XGoogle Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2cXitlSjtLc%253D&md5=e9644238a3c9bc239f0937d21d71a1a0Photonic band gaps in three dimensions: new layer-by-layer periodic structuresHo, K. M.; Chan, C. T.; Soukoulis, C. M.; Biswas, R.; Sigalas, M.Solid State Communications (1994), 89 (5), 413-16CODEN: SSCOA4; ISSN:0038-1098.A new 3-dimensional (3D) periodic dielec. structure constructed with layers of dielec. rods of circular, elliptical, or rectangular shape is introduced. This new structure possesses a full photonic band gap of appreciable frequency width. At midgap, an attenuation of 21 dB per unit cell is obtained. This gap remains open for refractive indexes n ≥ 1.9. Also, this new 3-dimensional layer structure potentially has the addnl. advantage that it can be easily fabricated using conventional microfabrication techniques on the scale of optical wavelengths.
- 19Maldovan, M.; Thomas, E. L. Diamond Structured Photonic Crystals. Nat. Mater. 2004, 3, 593– 600, DOI: 10.1038/nmat1201Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXntlGitbc%253D&md5=00313acbdaf468c9a7623c46502e08f3Diamond-structured photonic crystalsMaldovan, Martin; Thomas, Edwin L.Nature Materials (2004), 3 (9), 593-600CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)A review. Certain periodic dielec. structures can prohibit the propagation of light for all directions within a frequency range. These photonic crystals allow researchers to modify the interaction between electromagnetic fields and dielec. media from radio to optical wavelengths. Their technol. potential, such as the inhibition of spontaneous emission, enhancement of semiconductor lasers, and integration and miniaturization of optical components, makes the search for an easy-to-craft photonic crystal with a large bandgap a major field of study. This progress article surveys a collection of robust complete 3-dimensional dielec. photonic-bandgap structures for the visible and near-IR regimes based on the diamond morphol. together with their specific fabrication techniques. The basic origin of the complete photonic bandgap for the champion diamond morphol. is described in terms of dielec. modulations along principal directions. Progress in 3-dimensional interference lithog. for fabrication of near-champion diamond-based structures is also discussed.
- 20Leistikow, M. D.; Mosk, A. P.; Yeganegi, E.; Huisman, S. R.; Lagendijk, A.; Vos, W. L. Inhibited Spontaneous Emission of Quantum Dots Observed in a 3D Photonic Band Gap. Phys. Rev. Lett. 2011, 107, 193903, DOI: 10.1103/PhysRevLett.107.193903Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsV2ktbzL&md5=c6904314bd48aa11f64d00aad728b26cInhibited Spontaneous Emission of Quantum Dots Observed in a 3D Photonic Band GapLeistikow, M. D.; Mosk, A. P.; Yeganegi, E.; Huisman, S. R.; Lagendijk, A.; Vos, W. L.Physical Review Letters (2011), 107 (19), 193903/1-193903/5CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)We present time-resolved emission expts. of semiconductor quantum dots in silicon 3D inverse-woodpile photonic band gap crystals. A systematic study is made of crystals with a range of pore radii to tune the band gap relative to the emission frequency. The decay rates averaged over all dipole orientations are inhibited by a factor of 10 in the photonic band gap and enhanced up to 2× outside the gap, in agreement with theory. We discuss the effects of spatial inhomogeneity, nonradiative decay, and transition dipole orientations on the obsd. inhibition in the band gap.
- 21Devashish, D.; Hasan, S. B.; van der Vegt, J. J. W.; Vos, W. L. Reflectivity Calculated for a Three-Dimensional Silicon Photonic Band Gap Crystal with Finite Support. Phys. Rev. B: Condens. Matter Mater. Phys. 2017, 95, 155141, DOI: 10.1103/PhysRevB.95.155141Google ScholarThere is no corresponding record for this reference.
- 22Goldstein, J.; Newbury, D. E.; Joy, D. C.; Lyman, C. E.; Echlin, P.; Lifshim, E.; Sawyer, L.; Michael, J. R. Scanning Electron Microscopy and X-Ray Microanalysis; Springer: New York, 2003.Google ScholarThere is no corresponding record for this reference.
- 23Jacobsen, C.; Medewaldt, R.; Williams, S. In X-ray Microscopy and Spectromicroscopy; Thieme, J., Schmahl, G., Rudolph, D., Umbach, E., Eds.; Springer: New York, 1998; pp 197– 206.Google ScholarThere is no corresponding record for this reference.
- 24Misra, S.; Liu, N.; Nelson, J.; Hong, S. S.; Cui, Y.; Toney, M. In Situ X-Ray Diffraction Studies of (De)Lithiation Mechanism in Silicon Nanowire Anodes. ACS Nano 2012, 6, 5465– 5473, DOI: 10.1021/nn301339gGoogle Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XmsFGjtbs%253D&md5=b314a19360d8a47b8d600fc1b1fcd04eIn Situ X-ray Diffraction Studies of (De)lithiation Mechanism in Silicon Nanowire AnodesMisra, Sumohan; Liu, Nian; Nelson, Johanna; Hong, Seung Sae; Cui, Yi; Toney, Michael F.ACS Nano (2012), 6 (6), 5465-5473CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)Silicon is a promising anode material for Li-ion batteries due to its high theor. specific capacity. From previous work, silicon nanowires are known to undergo amorphorization during lithiation, and no cryst. Li-Si product has been obsd. In this work, we use an x-ray transparent battery cell to perform in situ synchrotron x-ray diffraction on silicon nanowires in real time during electrochem. cycling. At deep lithiation voltages the known metastable Li15Si4 phase forms, and we show that avoiding the formation of this phase, by modifying the silicon nanowire growth temp., improves the cycling performance of silicon nanowire anodes. Our results provide insight on the (de)lithiation mechanism and a correlation between phase evolution and electrochem. performance for silicon nanowire anodes.
- 25Stankevič, T.; Hilner, E.; Seiboth, F.; Ciechonski, R.; Vescovi, G.; Kryliouk, O.; Johansson, U.; Samuelson, L.; Wellenreuther, G.; Falkenberg, G.; Feidenhansl, R.; Mikkelsen, A. Fast Strain Mapping of Nanowire Light-Emitting Diodes Using Nanofocused X-Ray Beams. ACS Nano 2015, 9, 6978– 6984, DOI: 10.1021/acsnano.5b01291Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVKisbvM&md5=22b3626eda6347a1c6ed226e0650d7a1Fast Strain Mapping of Nanowire Light-Emitting Diodes Using Nanofocused X-ray BeamsStankevic, Tomas; Hilner, Emelie; Seiboth, Frank; Ciechonski, Rafal; Vescovi, Giuliano; Kryliouk, Olga; Johansson, Ulf; Samuelson, Lars; Wellenreuther, Gerd; Falkenberg, Gerald; Feidenhans'l, Robert; Mikkelsen, AndersACS Nano (2015), 9 (7), 6978-6984CODEN: ANCAC3; ISSN:1936-0851. (American Chemical Society)X-ray nanobeams are unique nondestructive probes that allow direct measurements of the nanoscale strain distribution and compn. inside the micrometer thick layered structures that are found in most electronic device architectures. However, the method is usually extremely time-consuming, and as a result, data sets are often constrained to a few or even single objects. Here we demonstrate that by special design of a nanofocused X-ray beam diffraction expt. we can (in a single 2D scan with no sample rotation) measure the individual strain and compn. profiles of many structures in an array of upright standing nanowires. We make use of the observation that in the generic nanowire device configuration, which is found in high-speed transistors, solar cells, and light-emitting diodes, each wire exhibits very small degrees of random tilts and twists toward the substrate. Although the tilt and twist are very small, they give a new contrast mechanism between different wires. In the present case, we image complex nanowires for nanoLED fabrication and compare to theor. simulations, demonstrating that this fast method is suitable for real nanostructured devices.
- 26Vos, W. L.; Megens, M.; van Kats, C. M.; Bösecke, P. X-Ray Diffraction of Photonic Colloidal Single Crystals. Langmuir 1997, 13, 6004– 6008, DOI: 10.1021/la970423nGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmvVals7w%253D&md5=f78655afedb2c7e0caa821b6956006f1X-ray Diffraction of Photonic Colloidal Single CrystalsVos, Willem L.; Megens, Mischa; van Kats, Carlos M.; Boesecke, PeterLangmuir (1997), 13 (23), 6004-6008CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The authors have resolved a great no. of Bragg peaks of photonic colloidal single crystals by synchrotron small angle x-ray scattering (SAXS). Charge-stabilized colloids form fcc. crystals at all densities up to ∼60 vol.%. The colloidal particles are highly ordered on their lattice sites, which confirms that these self-organizing materials are suitable building blocks for optical photonic matter. Synchrotron SAXS with two-dimensional detection is a powerful tool to study systems with length scales comparable to optical wavelengths.
- 27Shabalin, A. G.; Meijer, J.-M.; Dronyak, R.; Yefanov, O. M.; Singer, A.; Kurta, R. P.; Lorenz, U.; Gorobtsov, O. Y.; Dzhigaev, D.; Kalbfleisch, S.; Gulden, J.; Zozulya, A. V.; Sprung, M.; Petukhov, A. V.; Vartanyants, I. A. Revealing Three-Dimensional Structure of an Individual Colloidal Crystal Grain by Coherent X-Ray Diffractive Imaging. Phys. Rev. Lett. 2016, 117, 138002, DOI: 10.1103/PhysRevLett.117.138002Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXht1Gku7c%253D&md5=f1987dcca3b5b338e6717c75fdcffbdbRevealing three-dimensional structure of an individual colloidal crystal grain by coherent x-ray diffractive imagingShabalin, A. G.; Meijer, J.-M.; Dronyak, R.; Yefanov, O. M.; Singer, A.; Kurta, R. P.; Lorenz, U.; Gorobtsov, O. Y.; Dzhigaev, D.; Kalbfleisch, S.; Gulden, J.; Zozulya, A. V.; Sprung, M.; Petukhov, A. V.; Vartanyants, I. A.Physical Review Letters (2016), 117 (13), 138002/1-138002/6CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)We present results of a coherent x-ray diffractive imaging expt. performed on a single colloidal crystal grain. The full three-dimensional (3D) reciprocal space map measured by an azimuthal rotational scan contained several orders of Bragg reflections together with the coherent interference signal between them. Applying the iterative phase retrieval approach, the 3D structure of the crystal grain was reconstructed and positions of individual colloidal particles were resolved. As a result, an exact stacking sequence of hcp. layers including planar and linear defects were identified.
- 28Sakdinawat, A.; Attwood, D. Nanoscale X-Ray Imaging. Nat. Photonics 2010, 4, 840– 848, DOI: 10.1038/nphoton.2010.267Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhsVygs7jE&md5=e5a54791ee55916a851ac499006a5bd0Nanoscale X-ray imagingSakdinawat, Anne; Attwood, DavidNature Photonics (2010), 4 (12), 840-848CODEN: NPAHBY; ISSN:1749-4885. (Nature Publishing Group)Recent years have seen significant progress in the field of soft- and hard-X-ray microscopy, both tech., through developments in source, optics and imaging methodologies, and also scientifically, through a wide range of applications. While an ever-growing community is pursuing the extensive applications of today's available X-ray tools, other groups are investigating improvements in techniques, including new optics, higher spatial resolns., brighter compact sources and shorter-duration X-ray pulses. This Review covers recent work in the development of direct image-forming X-ray microscopy techniques and the relevant applications, including three-dimensional biol. tomog., dynamical processes in magnetic nanostructures, chem. speciation studies, industrial applications related to solar cells and batteries, and studies of archaeol. materials and historical works of art.
- 29Pollak, B. Experiences With Planography. Dis. Chest 1953, 24, 663– 669, DOI: 10.1378/chest.24.6.663Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADyaG2c%252FivVCrsQ%253D%253D&md5=7e4823b3842e60f9ed9e7d9fc9346ddeExperiences with planographyPOLLAK BDiseases of the chest (1953), 24 (6), 663-9 ISSN:0096-0217.There is no expanded citation for this reference.
- 30Cloetens, P.; Ludwig, W.; Baruchel, J.; van Dyck, D.; van Landuyt, J.; Guigay, J. P.; Schlenker, M. Holotomography: Quantative Phase Tomography with Micrometer Resolution Using Hard Synchrotron Radiation X Rays. Appl. Phys. Lett. 1999, 75, 2912– 2914, DOI: 10.1063/1.125225Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXmvFChurY%253D&md5=45b3236fa08a8f33e3de858d766ea383Holotomography. Quantitative phase tomography with micrometer resolution using hard synchrotron radiation x raysCloetens, P.; Ludwig, W.; Baruchel, J.; Van Dyck, D.; Van Landuyt, J.; Guigay, J. P.; Schlenker, M.Applied Physics Letters (1999), 75 (19), 2912-2914CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)Because the refractive index for hard x rays is slightly different from unity, the optical phase of a beam is affected by transmission through an object. Phase images can be obtained with extreme instrumental simplicity by simple propagation provided the beam is coherent. But, unlike absorption, the phase is not simply related to image brightness. A holog. reconstruction procedure combining images taken at different distances from the specimen was developed. It results in quant. phase mapping and, through assocn. with 3D reconstruction, in holotomog., the complete 3D mapping of the d. in a sample. This tool in the characterization of materials at the micrometer scale is uniquely suited to samples with low absorption contrast and radiation-sensitive systems.
- 31Mokso, R.; Cloetens, P.; Maire, E.; Ludwig, W.; Buffière, J.-Y. Nanoscale Zoom Tomography with Hard X-Rays Using Kirkpatrick-Baez Optics. Appl. Phys. Lett. 2007, 90, 144104, DOI: 10.1063/1.2719653Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXksV2jt70%253D&md5=4ac904d5c4c03a0c25c39b6dfe8f57f0Nanoscale zoom tomography with hard x-rays using Kirkpatrick-Baez opticsMokso, R.; Cloetens, P.; Maire, E.; Ludwig, W.; Buffiere, J.-Y.Applied Physics Letters (2007), 90 (14), 144104/1-144104/3CODEN: APPLAB; ISSN:0003-6951. (American Institute of Physics)To overcome the limitations in terms of spatial resoln. and field of view of existing tomog. techniques, a hard x-ray projection microscope is realized based on the sub-100-nm focus produced by Kirkpatrick-Baez optics. The sample is set at a small distance downstream of the focus and Fresnel diffraction patterns with variable magnification are recorded on a medium-resoln. detector. While the approach requires a specific phase retrieval procedure and correction for mirror imperfections, it allows zooming nondestructively into bulky samples. Quant. 3-dimensional nanoscale microscopy is demonstrated on an Al alloy in local tomog. mode.
- 32van den Broek, J. M.; Woldering, L. A.; Tjerkstra, R. W.; Segerink, F. B.; Setija, I. D.; Vos, W. L. Inverse-Woodpile Photonic Band Gap Crystals with a Cubic Diamond-Like Structure Made from Single Crystalline Silicon. Adv. Funct. Mater. 2012, 22, 25– 31, DOI: 10.1002/adfm.201101101Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXht1equ7vF&md5=0817d8cb2b0f4829f37fd7458ca448e4Inverse-Woodpile Photonic Band Gap Crystals with a Cubic Diamond-like Structure Made from Single-Crystalline Siliconvan den Broek, J. M.; Woldering, L. A.; Tjerkstra, R. W.; Segerink, F. B.; Setija, I. D.; Vos, W. L.Advanced Functional Materials (2012), 22 (1), 25-31CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)Three dimensional photonic band gap crystals with a cubic diamond-like symmetry are fabricated. These so-called inverse-woodpile nanostructures consist of 2 perpendicular sets of pores in single-crystal Si wafers and are made by complementary metal oxide-semiconductor (CMOS)-compatible methods. Both sets of pores have high aspect ratios and are made by deep reactive-ion etching. The mask for the 1st set of pores is defined in Cr by deep UV scan-and-step technol. The mask for the 2nd set of pores is patterned using an ion beam and carefully placed at an angle of 90° with an alignment precision of better than 30 nm. Crystals are made with pore radii between 135-186 nm with lattice parameters a 686. and c 488. nm such that a/c = √2; hence the structure is cubic. The crystals are characterized using SEM and x-ray diffraction. By milling away slices of crystal, the pores are analyzed in detail in both directions regarding depth, radius, tapering, shape, and alignment. Using optical reflectivity the crystals have broad reflectivity peaks in the near-IR frequency range, which includes the telecommunication range. The strong reflectivity confirms the high quality of the photonic crystals. Also the width of the reflectivity peaks agrees well with gaps in calcd. photonic band structures.
- 33Wu, B.; Kumar, A.; Pamarthy, S. High Aspect Ratio Silicon Etch: A Review. J. Appl. Phys. 2010, 108, 051101 DOI: 10.1063/1.3474652Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtFekt7bI&md5=876ed35bb39b9e9fd300e4c3466d53a2High aspect ratio silicon etch: A reviewWu, Banqiu; Kumar, Ajay; Pamarthy, SharmaJournal of Applied Physics (2010), 108 (5), 051101/1-051101/20CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)A review. High aspect ratio (HAR) Si etch is reviewed, including commonly used terms, history, main applications, different technol. methods, crit. challenges, and main theories of the technologies. Chronol., HAR Si etch was conducted using wet etch in soln., reactive ion etch (RIE) in low d. plasma, single-step etch at cryogenic conditions in inductively coupled plasma (ICP) combined with RIE, time-multiplexed deep silicon etch in ICP-RIE configuration reactor, and single-step etch in high d. plasma at room or near room temp. Key specifications are HAR, high etch rate, good trench sidewall profile with smooth surface, low aspect ratio dependent etch, and low etch loading effects. Until now, temp-multiplexed etch process is a popular industrial practice but the intrinsic scalloped profile of a time-multiplexed etch process, resulting from alternating between passivation and etch, poses a challenge. Previously, HAR Si etch was an application assocd. primarily with microelectromech. systems. In recent years, through-Si-via (TSV) etch applications for 3-dimensional integrated circuit stacking technol. has spurred research and development of this enabling technol. This potential large scale application requires HAR etch with high and stable throughput, controllable profile and surface properties, and low costs. (c) 2010 American Institute of Physics.
- 34Roman, B.; Bico, J. Elasto-Capillarity: Deforming an Elastic Structure with a Liquid Droplet. J. Phys.: Condens. Matter 2010, 22, 493101, DOI: 10.1088/0953-8984/22/49/493101Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXjs1ahuw%253D%253D&md5=0225b6f8365e3cb1cfd6b4a58563f692Elasto-capillarity: deforming an elastic structure with a liquid dropletRoman, B.; Bico, J.Journal of Physics: Condensed Matter (2010), 22 (49), 493101/1-493101/16CODEN: JCOMEL; ISSN:0953-8984. (Institute of Physics Publishing)A review. Although negligible at macroscopic scales, capillary forces become dominant as the sub-millimetric scales of micro-electro-mech. systems (MEMS) are considered. We review various situations, not limited to micro-technologies, where capillary forces are able to deform elastic structures. In particular, we define the different length scales that are relevant for 'elasto-capillary' problems. We focus on the case of slender structures (lamellae, rods and sheets) and describe the size of a bundle of wet hair, the condition for a flexible rod to pierce a liq. interface or the fate of a liq. droplet deposited on a flexible thin sheet. These results can be generalized to similar situations involving adhesion or fracture energy, which widens the scope of possible applications from biol. systems, to stiction issues in micro-fabrication processes, the manufg. of 3D microstructures or the formation of blisters in thin film coatings.
- 35Chen, Y. C.; Geddes, J. B.; Yin, L.; Wiltzius, P.; Braun, P. V. X-Ray Computed Tomography of Holographically Fabricated Three-Dimensional Photonic Crystals. Adv. Mater. 2012, 24, 2863– 2868, DOI: 10.1002/adma.201200411Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XmtlWktLo%253D&md5=2eecfde5a01b3cb4c07d631153351196X-Ray Computed Tomography of Holographically Fabricated Three-Dimensional Photonic CrystalsChen, Ying-Chieh; Geddes, Joseph B.; Yin, Leilei; Wiltzius, Pierre; Braun, Paul V.Advanced Materials (Weinheim, Germany) (2012), 24 (21), 2863-2868CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)The authors have demonstrated real-space 3D imaging of holog. defined photonic crystals (PC) via x-ray computed tomog. (CT) on a HfO2 in-filled SU-8-based PC sample. To the best of the authors knowledge, this study is the first use of x-ray CT to characterize the morphol. of a 3D PC. The reconstructed structure used for calcn. of reflectance spectra agreed with the measured spectra. The geometry of the reconstructed structure was compared with the previously reported modeled structure. The two structures exhibited 85 % geometric agreement between them, and the observable differences explained the relatively higher reflectance spectra displayed by the reconstructed structure over the modeled structure. By using x-ray tomog. to measure the fabricated PC, it is now possible to investigate the deformation process from an as made PC through processing. Several factors were considered to account for this deformation and may include crosslink d. variations and material loss during development. This improved understanding of the correlation between the interference pattern and final fabricated PC structure can facilitate the design of PCs, including those contg. engineered embedded defects, for photonic applications.
- 36Holler, M.; Guizar-Sicairos, M.; Tsai, E. H. R.; Dinapoli, R.; Müller, E.; Bunk, O.; Raabe, J.; Aeppli, G. High Resolution Non-Destructive Three Dimensional Imaging of Integrated Circuits. Nature (London, U. K.) 2017, 543, 402– 406, DOI: 10.1038/nature21698Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXlslensLs%253D&md5=ee2d3b0da96c9d8b5ce45caf33fe1a25High-resolution non-destructive three-dimensional imaging of integrated circuitsHoller, Mirko; Guizar-Sicairos, Manuel; Tsai, Esther H. R.; Dinapoli, Roberto; Muller, Elisabeth; Bunk, Oliver; Raabe, Jorg; Aeppli, GabrielNature (London, United Kingdom) (2017), 543 (7645), 402-406CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Modern nanoelectronics has advanced to a point at which it is impossible to image entire devices and their interconnections non-destructively because of their small feature sizes and the complex three-dimensional structures resulting from their integration on a chip. This metrol. gap implies a lack of direct feedback between design and manufg. processes, and hampers quality control during prodn., shipment and use. Here we demonstrate that X-ray ptychog.-a high-resoln. coherent diffractive imaging technique-can create three-dimensional images of integrated circuits of known and unknown designs with a lateral resoln. in all directions down to 14.6 nm. We obtained detailed device geometries and corresponding elemental maps, and show how the devices are integrated with each other to form the chip. Our expts. represent a major advance in chip inspection and reverse engineering over the traditional destructive electron microscopy and ion milling techniques. Foreseeable developments in X-ray sources, optics and detectors, as well as adoption of an instrument geometry optimized for planar rather than cylindrical samples, could lead to a thousand-fold increase in efficiency, with concomitant redns. in scan times and voxel sizes.
- 37Furlan, K. P.; Larsson, E.; Diaz, A.; Holler, M.; Krekeler, T.; Ritter, M.; Petrov, A. Y.; Eich, M.; Blick, R.; Schneider, G. A.; Greving, I.; Zierold, R.; Janen, R. Photonic Materials for HighTemperature Applications: Synthesis and Characterization by X-Ray Ptychographic Tomography. Appl. Mater. Today 2018, 13, 359– 369, DOI: 10.1016/j.apmt.2018.10.002Google ScholarThere is no corresponding record for this reference.
- 38da Silva, J. C.; Guizar-Sicairos, M.; Holler, M.; Diaz, A.; van Bokhoven, J. A.; Bunk, O.; Menzel, A. Quantitative Region-Of-Interest Tomography Using Variable Field of View. Opt. Express 2018, 26, 16752– 16768, DOI: 10.1364/OE.26.016752Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitlyjsLvP&md5=7e47b7c3a184c51b987a8c916f2458aeQuantitative region-of-interest tomography using variable field of viewDa Silva, J. C.; Guizar-Sicairos, M.; Holler, M.; Diaz, A.; Van Bokhoven, J. A.; Bunk, O.; Menzel, A.Optics Express (2018), 26 (13), 16752-16768CODEN: OPEXFF; ISSN:1094-4087. (Optical Society of America)In X-ray computed tomog., the task of imaging only a local region of interest (ROI) inside a larger sample is very important. However, without a priori information, this ROI cannot be exactly reconstructed using only the image data limited to the ROI. We propose here an approach of region-of-interest tomog., which reconstructs a ROI within an object from projections of different fields of view acquired on a specific angular sampling scheme in the same tomog. expt. We present a stable procedure that not only yields high-quality images of the ROI but keeps as well the quant. contrast on the reconstructed images. In addn., we analyze the min. no. of projections required for ROI tomog. from the point of view of the band region of the Radon transform, which confirms this no. must be estd. based on the size of the entire object and not only on the size of the ROI.
- 39Guizar-Sicairos, M.; Johnson, I.; Diaz, A.; Holler, M.; Karvinen, P.; Stadler, H. C.; Dinapoli, R.; Bunk, O.; Menzel, A. HighThroughput Ptychography Using Eiger: Scanning X-Ray Nano-Imaging of Extended Regions. Opt. Express 2014, 22, 14859– 14870, DOI: 10.1364/OE.22.014859Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC2cfot1GhtA%253D%253D&md5=f70b5ac076f9a1ad08dd5d145ed48aadHigh-throughput ptychography using Eiger: scanning X-ray nano-imaging of extended regionsGuizar-Sicairos Manuel; Johnson Ian; Diaz Ana; Holler Mirko; Karvinen Petri; Stadler Hans-Christian; Dinapoli Roberto; Bunk Oliver; Menzel AndreasOptics express (2014), 22 (12), 14859-70 ISSN:.The smaller pixel size and high frame rate of next-generation photon counting pixel detectors opens new opportunities for the application of X-ray coherent diffractive imaging (CDI). In this manuscript we demonstrate fast image acquisition for ptychography using an Eiger detector. We achieve above 25,000 resolution elements per second, or an effective dwell time of 40 μs per resolution element, when imaging a 500 μm × 290 μm region of an integrated electronic circuit with 41 nm resolution. We further present the application of a scheme of sharing information between image parts that allows the field of view to exceed the range of the piezoelectric scanning system and requirements on the stability of the illumination to be relaxed.
- 40Tjerkstra, R. W.; Woldering, L. A.; van den Broek, J. M.; Roozeboom, F.; Setija, I. D.; Vos, W. L. Method to Pattern Etch Masks in Two Inclined Planes for Three Dimensional Nano- and Microfabricationy. J. Vac. Sci. Technol., B: Nanotechnol. Microelectron.: Mater., Process., Meas., Phenom. 2011, 29, 061604 DOI: 10.1116/1.3662000Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xht1aqurs%253D&md5=a1afacd4116397991fb37b020010a00fMethod to pattern etch masks in two inclined planes for three-dimensional nano- and microfabricationTjerkstra, R. Willem; Woldering, Leon A.; van den Broek, Johanna M.; Roozeboom, Fred; Setija, Irwan D.; Vos, Willem L.Journal of Vacuum Science & Technology, B: Nanotechnology & Microelectronics: Materials, Processing, Measurement, & Phenomena (2011), 29 (6), 061604/1-061604/8CODEN: JVSTCN ISSN:. (American Institute of Physics)The authors present a method to pattern etch masks for arbitrary nano- and microstructures on different, inclined planes of a sample. Our method allows std. CMOS fabrication techniques to be used in different inclined planes; thus yielding three-dimensional structures with a network topol. The method involves processing of the sample in a first plane, followed by mounting the prepd. sample in a specially designed silicon holder wafer such that the second, inclined plane is exposed to continued processing. As a proof of principle we demonstrate the fabrication of a patterned chromium etch mask for three-dimensional photonic crystals in silicon. The etch mask is made on the 90° inclined plane of a silicon sample that already contains high aspect ratio nanopores. The etch mask is carefully aligned with respect to these pores, with a high translational accuracy of <30 nm along the y-axis and a high rotational accuracy of 0.71° around the z-axis of the crystal. Such high alignment precisions are crucial for nanophotonics and for sub-micrometer applications in general. Although we limit ourselves to processing on two planes of a sample, it is in principle possible to repeat the presented method on more planes. The authors foresee potential applications of this technique in, e.g., microfluidics, photonics, and three-dimensional silicon electronics. (c) 2011 American Institute of Physics.
- 41Grishina, D. A.; Harteveld, C. A. M.; Woldering, L. A.; Vos, W. L. Method to Make a Single-Step Etch Mask for 3D Monolithic Nanostructures. Nanotechnology 2015, 26, 505302, DOI: 10.1088/0957-4484/26/50/505302Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhtVOlu7vP&md5=6fa2f6a94c1fb320e73ef1a5d0e0c85aMethod for making a single-step etch mask for 3D monolithic nanostructuresGrishina, D. A.; Harteveld, C. A. M.; Woldering, L. A.; Vos, W. L.Nanotechnology (2015), 26 (50), 505302/1-505302/10CODEN: NNOTER; ISSN:1361-6528. (IOP Publishing Ltd.)Current nanostructure fabrication by etching is usually limited to planar structures as they are defined by a planar mask. The realization of three-dimensional (3D) nanostructures by etching requires technologies beyond planar masks. We present a method for fabricating a 3D mask that allows one to etch three-dimensional monolithic nanostructures using only CMOS-compatible processes. The mask is written in a hard-mask layer that is deposited on two adjacent inclined surfaces of a Si wafer. By projecting in a single step two different 2D patterns within one 3D mask on the two inclined surfaces, the mutual alignment between the patterns is ensured. Thereby after the mask pattern is defined, the etching of deep pores in two oblique directions yields a three-dimensional structure in Si. As a proof of concept we demonstrate 3D mask fabrication for three-dimensional diamond-like photonic band gap crystals in silicon. The fabricated crystals reveal a broad stop gap in optical reflectivity measurements. We propose how 3D nanostructures with five different Bravais lattices can be realized, namely cubic, tetragonal, orthorhombic, monoclinic and hexagonal, and demonstrate a mask for a 3D hexagonal crystal. We also demonstrate the mask for a diamond-structure crystal with a 3D array of cavities. In general, the 2D patterns on the different surfaces can be completely independently structured and still be in perfect mutual alignment. Indeed, we observe an alignment accuracy of better than 3.0 nm between the 2D mask patterns on the inclined surfaces, which permits one to etch welldefined monolithic 3D nanostructures.
- 42Cesar da Silva, J.; Pacureanu, A.; Yang, Y.; Bohic, S.; Morawe, C.; Barrett, R.; Cloetens, P. Efficient Concentration of High-Energy XRays for Diffraction-Limited Imaging Resolution. Optica 2017, 4, 492– 495, DOI: 10.1364/OPTICA.4.000492Google ScholarThere is no corresponding record for this reference.
- 43Gabor, D. A New Microscopic Principle. Nature (London, U. K.) 1948, 161, 777– 778, DOI: 10.1038/161777a0Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADyaH1c%252FgsVSgug%253D%253D&md5=66f5aa921ddb675bc2696abb775f2166A new microscopic principleGABOR DNature (1948), 161 (4098), 777 ISSN:0028-0836.There is no expanded citation for this reference.
- 44Pogany, D.; Gao, A.; Wilkins, S. W. Contrast and Resolution in Imaging with a Microfocus X-Ray Source. Rev. Sci. Instrum. 1997, 68, 2774– 2782, DOI: 10.1063/1.1148194Google Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXkslWnu7Y%253D&md5=1f39904b428a60172cf3ae94838fe3f7Contrast and resolution in imaging with a microfocus x-ray sourcePogany, A.; Gao, D.; Wilkins, S. W.Review of Scientific Instruments (1997), 68 (7), 2774-2782CODEN: RSINAK; ISSN:0034-6748. (American Institute of Physics)A simple general treatment of x-ray image formation by Fresnel diffraction is presented; the image can alternatively be considered as an in-line hologram. Particular consideration is given to phase-contrast microscopy and imaging using hard x-rays. The theory makes use of the optical transfer function in a similar way to that used in the theory of electron microscope imaging. Resoln. and contrast are the criteria used to specify the visibility of an image. Resoln. in turn depends primarily on the spatial coherence of the illumination, with chromatic coherence of lesser importance. Thus broadband microfocus sources can give useful phase-contrast images. Both plane-and spherical-wave conditions are explicitly considered as limiting cases appropriate to macroscopic imaging and microscopy, resp., while intermediate cases may also be of practical interest. Some results are presented for x-ray images showing phase contrast.
- 45Paganin, D. Coherent X-ray Optics; Oxford University Press: Oxford, 2006.Google ScholarThere is no corresponding record for this reference.
- 46Goodman, J. W. Introduction to Fourier Optics, 3rd ed.; Roberts & Co: Englewood, CO, 2005.Google ScholarThere is no corresponding record for this reference.
- 47Paganin, D.; Mayo, S. C.; Gureyev, T. E.; Miller, P. R.; Wilkins, S. W. Simultaneous Phase and Amplitude Extraction from a Single Defocused Image of a Homogeneous Object. J. Microsc. 2002, 206, 33– 40, DOI: 10.1046/j.1365-2818.2002.01010.xGoogle Scholar47https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BD383mtVWmtg%253D%253D&md5=87e8b3e1d788a6446f03db60666ff48dSimultaneous phase and amplitude extraction from a single defocused image of a homogeneous objectPaganin D; Mayo S C; Gureyev T E; Miller P R; Wilkins S WJournal of microscopy (2002), 206 (Pt 1), 33-40 ISSN:0022-2720.We demonstrate simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object. Subject to the assumptions explicitly stated in the derivation, the algorithm solves the twin-image problem of in-line holography and is capable of analysing data obtained using X-ray microscopy, electron microscopy, neutron microscopy or visible-light microscopy, especially as they relate to defocus and point projection methods. Our simple, robust, non-iterative and computationally efficient method is applied to data obtained using an X-ray phase contrast ultramicroscope.
- 48Hounsfield, G. Computerized Transverse Axial Scanning (Tomography): I. Description of System. Br. J. Radiol. 1973, 46, 1016– 1022, DOI: 10.1259/0007-1285-46-552-1016Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADyaE2c%252Fkt1Cjtw%253D%253D&md5=6f6b1e52cbb2af6b4734b2b11e7f1869Computerized transverse axial scanning (tomography). 1. Description of systemHounsfield G NThe British journal of radiology (1973), 46 (552), 1016-22 ISSN:0007-1285.There is no expanded citation for this reference.
- 49Herman, G. T. Fundamentals of Computerized Tomography, 2nd ed.; Springer: London, 2009.Google ScholarThere is no corresponding record for this reference.
- 50Mirone, A.; Brun, E.; Gouillart, E.; Tafforeau, P.; Kieffer, J. The pyhst2 Hybrid Distributed Code for High Speed Tomographic Reconstruction with Iterative Reconstruction and a Priori Knowledge Capabilities. Nucl. Instrum. Methods Phys. Res., Sect. B 2014, 324, 41– 48, DOI: 10.1016/j.nimb.2013.09.030Google Scholar50https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhslSktrw%253D&md5=1fbdebda8990e395da588222496a6ad2The PyHST2 hybrid distributed code for high speed tomographic reconstruction with iterative reconstruction and a priori knowledge capabilitiesMirone, Alessandro; Brun, Emmanuel; Gouillart, Emmanuelle; Tafforeau, Paul; Kieffer, JeromeNuclear Instruments & Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms (2014), 324 (), 41-48CODEN: NIMBEU; ISSN:0168-583X. (Elsevier B.V.)We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomog. This code has been engineered to sustain the high data flow typical of the 3rd generation synchrotron facilities (10 terabytes per expt.) by adopting a distributed and pipelined architecture. The code implements, beside a default filtered backprojection reconstruction, iterative reconstruction techniques with a priori knowledge. These latter are used to improve the reconstruction quality or in order to reduce the required data vol. or the deposited dose to the sample and reach a given quality goal. The implemented a priori knowledge techniques are based on the total variation penalization and a new recently found convex functional which is based on overlapping patches. We give details of the different methods and discuss how they are implemented in the PyHST2 code, which is distributed under free license. We provide methods for estg., in the absence of ground-truth data, the optimal parameters values for a priori techniques.
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- 52Huisman, S. R.; Nair, R.; Woldering, L. A.; Leistikow, M. D.; Mosk, A. P.; Vos, W. L. Signature of a Three-Dimensional Photonic Band Bap Observed on Silicon Inverse Woodpile Photonic Crystals. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 83, 205313, DOI: 10.1103/PhysRevB.83.205313Google Scholar52https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXotVyktLc%253D&md5=40248dab9957cbdfc59c8f8fa93e590fSignature of a three-dimensional photonic band gap observed on silicon inverse woodpile photonic crystalsHuisman, Simon R.; Nair, Rajesh V.; Woldering, Leon A.; Leistikow, Merel D.; Mosk, Allard P.; Vos, Willem L.Physical Review B: Condensed Matter and Materials Physics (2011), 83 (20), 205313/1-205313/7CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)The authors have studied the reflectivity of CMOS-compatible 3-dimensional Si inverse woodpile photonic crystals at near-IR frequencies. Polarization-resolved reflectivity spectra were obtained from 2 orthogonal crystal surfaces using an objective with a high numerical aperture. The spectra reveal broad peaks with max. reflectivity of 67% that are independent of the spatial position on the crystals. The spectrally overlapping reflectivity peaks for all directions and polarizations form the signature of a broad photonic band gap with a relative bandwidth up to 16%. This signature is supported with stop gaps in plane-wave band-structure calcns. and with the frequency region of the expected band gap.
- 53Adhikary, M.; Uppu, R.; Harteveld, C. A. M.; Grishina, D. A.; Vos, W. L. Experimental Probe of a Complete 3D Photonic Band Gap. arXiv.org 1909.01899 2019.Google ScholarThere is no corresponding record for this reference.
- 54Johnson, S. G.; Joannopoulos, J. D. Block Iterative Frequency-Domain Methods for Maxwells Equations in a Planewave Basis. Opt. Express 2001, 8, 173– 190, DOI: 10.1364/OE.8.000173Google Scholar54https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BD1MzisVSjsw%253D%253D&md5=494fb35704bb8259090be8a03106c65aBlock-iterative frequency-domain methods for Maxwell's equations in a planewave basisJohnson S; Joannopoulos JOptics express (2001), 8 (3), 173-90 ISSN:.We describe a fully-vectorial, three-dimensional algorithm to compute the definite-frequency eigenstates of Maxwell's equations in arbitrary periodic dielectric structures, including systems with anisotropy (birefringence) or magnetic materials, using preconditioned block-iterative eigensolvers in a planewave basis. Favorable scaling with the system size and the number of computed bands is exhibited. We propose a new effective dielectric tensor for anisotropic structures, and demonstrate that O Delta x;2 convergence can be achieved even in systems with sharp material discontinuities. We show how it is possible to solve for interior eigenvalues, such as localized defect modes, without computing the many underlying eigenstates. Preconditioned conjugate-gradient Rayleigh-quotient minimization is compared with the Davidson method for eigensolution, and a number of iteration variants and preconditioners are characterized. Our implementation is freely available on the Web.
Supporting Information
Supporting Information
ARTICLE SECTIONSThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnano.9b05519.
Movie S1: Color rendering of the rotating “good” crystal (AVI)
Movie S2: Black and white cross sections of the “good” sample (AVI)
Movie S3: Black and white cross sections of the “good” sample (high resolution, emphasis on the surface) (AVI)
Movie S4: Black and white cross sections of the “bad” sample (AVI)
Movie S5: Black and white cross sections of the “ugly” sample (AVI)
CMOS compatibility, details of the reflectivity setup, details of the theory, features of the reconstructed crystals (PDF)
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