Objective . To enable practical interferometry-based phase contrast CT using standard incoherent x-ray sources, we propose an imaging system where the analyzer grating is replaced by a high-resolution detector. Since there is no need to perform multiple exposures (with the analyzer grating at different positions) at each scan angle, this scheme is compatible with continuous-rotation CT apparatus, and has the potential to reduce patient radiation dose and patient motion artifacts. Approach . Grating-based x-ray interferometry is a well-studied technique for imaging soft tissues and highly scattering objects embedded in such tissues. In addition to the traditional x-ray absorption-based image, this technique allows reconstruction of the object phase and small-angle scattering information. When using conventional incoherent, polychromatic, hard x-ray tubes as sources, three gratings are usually employed. To sufficiently resolve the pattern generated in these interferometers with contemporary x-ray detectors, an analyzer grating is used, and consequently multiple images need to be acquired for each view angle. This adds complexity to the imaging system, slows image acquisition and thus increases sensitivity to patient motion, and is not dose efficient. By simulating image formation based on wave propagation, and proposing a novel phase retrieval algorithm based on a virtual grating, we assess the potential of a analyzer-grating-free system to overcome these limitations. Main results . We demonstrate that the removal of the analyzer-grating can produce equal image contrast-to-noise ratio at reduced dose (by a factor of 5), without prolonging scan duration. Significance. By demonstrating that an analyzer-free CT system, in conjuction with an efficient phase retrieval algorithm, can overcome the prohibitive dose and workflow penalties associated grating-stepping, an alternative path towards realizing clinical inteferometric CT appears possible.

The photonic band structure of plasmonic and nanophotonic materials and devices can be controlled by physical features much smaller than the optical diffraction limit. We present a methodology to correlate nanoscale structure to the photonic band structure directly using the cathodoluminescence (CL) signal generated by a sample in the scanning electron microscope. Further to conventional electron microscope imaging, we record the wavelength- and angular- distributions of luminescence in a highly- parallelized manner. The result is a wavelength- and angle- resolved data cube, which was transformed to observe the emission intensity in the energy-momentum basis revealing the photonic band structure.

Journal Article Improved Microanalysis Using Cathodoluminescence Spectrum Imaging with Higher Spatial Sampling Get access David Stowe, David Stowe Gatan, Inc., Pleasanton, California, United States Search for other works by this author on: Oxford Academic Google Scholar Jonathan Lee, Jonathan Lee Gatan, Inc., Pleasanton, California, United States Search for other works by this author on: Oxford Academic Google Scholar Michael Bertilson, Michael Bertilson Gatan, Inc., Pleasanton, California, United States Search for other works by this author on: Oxford Academic Google Scholar Salvatore Fahey, Salvatore Fahey Gatan, Inc., Pleasanton, California, United States Search for other works by this author on: Oxford Academic Google Scholar John Hunt John Hunt Gatan, Inc., Pleasanton, California, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 26, Issue S2, 1 August 2020, Pages 2698–2699, https://doi.org/10.1017/S1431927620022461 Published: 01 August 2020

Journal Article Use of Wavelength- and Angle-Resolved Cathodoluminescence for Spectroscopic Analysis of the Emission Pattern of a Nitride Semiconductor Micro Pillar Array Get access J Lee, J Lee Gatan Inc, Pleasanton, California, United States of America Search for other works by this author on: Oxford Academic Google Scholar M Bertilson, M Bertilson Gatan Inc, Pleasanton, California, United States of America Search for other works by this author on: Oxford Academic Google Scholar DJ Stowe, DJ Stowe Gatan Inc, Pleasanton, California, United States of America Corresponding author: dstowe@gatan.com Search for other works by this author on: Oxford Academic Google Scholar T Worsley, T Worsley Gatan Inc, Pleasanton, California, United States of America Search for other works by this author on: Oxford Academic Google Scholar JA Hunt JA Hunt Gatan Inc, Pleasanton, California, United States of America Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 25, Issue S2, 1 August 2019, Pages 520–521, https://doi.org/10.1017/S1431927619003337 Published: 01 August 2019

Researchers are actively seeking new ways to direct and enhance the radiation or absorption of lightemitting and light-harvesting devices [e.g. 1]. One highly promising approach is to make use of nanostructured surfaces or objects whose interactions with light may be modified through a change of their size, shape, or composition. Characterization of the optical properties of materials with spatial resolution better than the diffraction limit of light is required to further our understanding of light-matter interactions in nanostructured materials and devices. Thus, the technique of cathodoluminescence (CL) in the scanning electron microscope (SEM) has gained great interest due to the ability to excite optical processes with a sub-nanometer probe of (fast) electrons, correlating optical information with sample morphology, composition and crystal structure at the nanoscale [e.g. 2].

Journal Article Advances in (and a Brief History of) Cathodoluminescence Microscopy Get access DJ Stowe, DJ Stowe Gatan Inc., 25 Nuffield Way, Abingdon, Oxon., UK Search for other works by this author on: Oxford Academic Google Scholar M Bertilson, M Bertilson Gatan Inc., 5794 W Las Positas Blvd, Pleasanton, USA Search for other works by this author on: Oxford Academic Google Scholar JA Hunt JA Hunt Gatan Inc., 5794 W Las Positas Blvd, Pleasanton, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 23, Issue S1, 1 July 2017, Pages 1034–1035, https://doi.org/10.1017/S1431927617005839 Published: 04 August 2017

Transmission X-ray microscopy is a uniquely suited technique for studies of environmental colloids since it allows imaging in aqueous media with high spatial resolution, presently down to the 20nm range. Such nano-scale morphological description of these high-specific-surface-area compounds show promise for improved understanding of soils, sediments or groundwater aquifers. However, present high-quality X-ray microscopes are located at synchrotron radiation facilities resulting in limited applicability and accessibility for colloid scientists. Here we investigate the applicability of a laboratory-scale transmission X-ray microscope for studies of colloids of the environment. The microscope is based on a laser-plasma source in combination with multilayer and zone plate optics. Samples are held at atmospheric pressure in their natural wet state. We show images revealing the nano-scale morphology of the clay nontronite, soils such as chernozem and luvisol, and the mineral hematite, an iron oxide. Comparative studies of dried substances clearly show the need for imaging in the wet state. The image quality approaches that of synchrotron-based microscopes, albeit at longer exposure times. Stereo imaging is investigated as a means for giving 3D information with shorter exposure times than tomography requires. Finally the future development of the laboratory X-ray microscope is discussed, especially with regard to the reduction of exposure times.

Lens-based water-window X-ray microscopy allows two- and three-dimensional (2D and 3D) imaging of intact unstained cells in their near-native state with unprecedented contrast and resolution. Cryofixation is essential to avoid radiation damage to the sample. Present cryo X-ray microscopes rely on synchrotron radiation sources, thereby limiting the accessibility for a wider community of biologists. In the present paper we demonstrate water-window cryo X-ray microscopy with a laboratory-source-based arrangement. The microscope relies on a λ = 2.48-nm liquid-jet high-brightness laser-plasma source, normal-incidence multilayer condenser optics, 30-nm zone-plate optics, and a cryo sample chamber. We demonstrate 2D imaging of test patterns, and intact unstained yeast, protozoan parasites and mammalian cells. Overview 3D information is obtained by stereo imaging while complete 3D microscopy is provided by full tomographic reconstruction. The laboratory microscope image quality approaches that of the synchrotron microscopes, but with longer exposure times. The experimental image quality is analyzed from a numerical wave-propagation model of the imaging system and a path to reach synchrotron-like exposure times in laboratory microscopy is outlined.

We present a numerical image-formation model for investigating the influence of partial coherence, sample thickness and depth-of-focus on the accuracy of tomographic reconstructions in transmission x-ray microscopes. The model combines wave propagation through the object by finite difference techniques with Fourier methods. We include a ray-tracing model to analyse the origin of detrimental stray light in zone plate-based x-ray microscopes. These models allow optimization of x-ray microscopy systems for quantitative tomographic imaging of thick objects. Results show that both the depth-of-focus and the reconstructed local absorption coefficient are highly dependent on the degree of coherence of the optical system.

Zone plates are used as objectives for high-resolution x-ray microscopy. Both high resolution and high diffraction efficiency are crucial parameters for the performance of the lens. In this article, the authors demonstrate the fabrication of high-resolution soft x-ray zone plates with improved diffraction efficiency by combining a nanofabrication process for high resolution with a process for high diffraction efficiency. High-resolution Ni zone plates are fabricated by applying cold development of electron-beam-patterned ZEP 7000 in a trilayer-resist process combined with Ni-electroplating. High-diffraction-efficiency Ni-Ge zone plates are realized by fabricating the Ni zone plate on a Ge film and then using the finished zone plate as etch mask for anisotropic CHF3 reactive ion etching into the underlying Ge, resulting in a Ni-Ge zone plate with improved aspect ratio and zone plate efficiency. Ni-Ge zone plates with 13 nm outermost zone width composed of 35 nm Ni on top of 45 nm Ge were fabricated. For comparable Ni and Ni-Ge zone plates with an outermost zone width of 15 nm, the diffraction efficiency was measured to be 2.4% and 4.3%, respectively, i.e., an enhancement of a factor of 2. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3520457]

X-rays allow quantitative high-spatial-resolution three-dimensional (3D) imaging of intact unstained cells. Such 3D imaging is provided by soft x-ray lens-based methods (water-window cryo tomograph ...

X‐ray wavefront propagation is a powerful technique when simulating the performance of x‐ray optical components. Using various numerical methods, interesting parameters such as focusing capability and efficiency can be investigated. Here we present the toolbox DiffractX, implemented in MATLAB. It contains many different wave propagation methods for the simulation of diffractive x‐ray optics, including Fresnel propagation, the finite difference method (FDM), the thin object approximation, the rigorous coupled wave theory (RCWT), and the finite element method (FEM). All tools are accessed through a graphical interface, making the design of simulations fast and intuitive, even for users with little or no programming experience. The tools have been utilized to characterize realistic as well as idealized optical components. This will aid further developments of diffractive x‐ray optics.

Using X-ray microscopy and spectromicroscopy, vascular smooth muscle cells (VSMCs) were imaged, prepared without using additional embedding material or staining, but by applying simple, noncryo fixation techniques. The cells were imaged with a compact source transmission X-ray microscope and a scanning transmission X-ray microscope (STXM). With the STXM, spectromicroscopy was performed at the C K-edge and the Ca L(III,II)-edges. VSMCs were chosen because of their high amount of actin stress fibers, so that the actin cytoskeleton should be visible. Other parts of the cell, such as the nucleus and organelles, were also identified from the micrographs. Both in the spectra and the images, the effects of the different preparation procedures were observable. Furthermore, Ca hotspots were detected and their density is determined.

Soft-x-ray cryotomography allows quantitative and high-resolution three-dimensional imaging of intact unstained cells. To date, the method relies on synchrotron-radiation sources, which limits accessibility for researchers. Here we present a laboratory water-window microscope for cryotomography. It is based on a λ=2.48 nm liquid-jet laser-plasma source, a normal-incidence multilayer condenser, a 30 nm zone-plate objective, and a cryotilt sample holder. We demonstrate high-resolution imaging, as well as quantitative tomographic imaging, of frozen intact cells. The reconstructed tomogram of the intracellular local absorption coefficient shows details down to ∼100 nm.

In this paper the latest efforts to improve our nanofabrication process for soft x‐ray zone plates is presented. The resolving power, which is proportional to the smallest outermost zone width of the zone plate, is increased by introducing cold development of the electron beam resist that is used for the patterning. With this process we have fabricated Ni zone plates with 13‐nm outermost zone and shown potential for making 11‐nm half‐pitch lines in the electron beam resist. Maintaining the diffraction efficiency of the zone plate is a great concern when the outermost zone width is decreased. To resolve this problem we have developed the so‐called Ni‐Ge zone plate in which the zone plate is build up by Ni and Ge, resulting in an increase of the diffraction efficiency. In a proof‐of‐principle experiment with 25‐nm Ni‐Ge zone plates, we have shown a doubling of the diffraction efficiency. When combined with cold development, the Ni‐Ge process has been shown to work down to 16‐nm half‐pitch. It is plausible that further refinement of the process will make it possible to go to 10‐nm outermost zone widths.

We demonstrate two nanofabrication methods which improve the diffraction efficiency of high-resolution soft X-ray nickel zone plates. First, pulse electroplating is shown to result in uniform diffraction efficiency over the entire zone-plate area. A resulting enhancement of the total efficiency of 20% compared to conventional DC plating was measured. Second, we demonstrate that a high-resolution cold development process can be combined with efficiency-enhancing dry etching into an underlying germanium film. We present 16 nm half-pitch gratings composed of 50 nm nickel on top of 50 nm germanium.

For nearly all elements, the real part, d, of the complex index of refraction n (n = 1 − δ + iβ) is larger than the imaginary part, β, in the x-ray region. Since only β is used in absorption contrast, phase-contrast imaging techniques which give access to δ are very important. In this paper we present two different implementations of phase contrast in our compact soft x-ray microscope, differential-interference contrast and Zernike phase contrast.

This article presents a fabrication process for soft x-ray zone plates in which nickel and germanium are combined to achieve high diffraction efficiency. A nickel zone plate is first fabricated on a germanium film and then used as a hardmask for a CHF(3)-plasma etch into the germanium. Zone plates with 50-60 nm nickel and 110-150 nm of germanium are presented. The measured diffraction efficiencies were 10%-11% at lambda=2.88 nm, which shows that high efficiency is possible even with thin nickel. Thus, the method has a potential for improving the efficiency of high-resolution zone plates for which the high-aspect-ratio structuring of nickel is difficult.