Fresnel zone plate with apodized aperture for hard X-ray Gaussian beam optics

Observation of water droplets in microporous layers for polymer electrolyte fuel cells by X-ray computed nano-tomography

An X-ray computed nano-tomography (nano-CT) system has been established at the BL33XU beamline of SPring-8. The optical system consists of pseudo-Köhler illumination with a sector condenser zone plate, an apodization Fresnel zone plate as the objective lens, and a Zernike phase plate. The imaging detector is a fiber-coupling type X-ray camera. The performance of the X-ray nano-CT system was confirmed by imaging an X-ray test chart. The system was subsequently applied to the observation of a microporous layer for polymer electrolyte fuel cells and a simulated microporous layer including liquid water. The nano-CT system, which can perform a computed tomography measurement in less than 4 min, allowed visualization of a spherical water droplet produced in the microporous layer. In the present study, the shape of water droplets in a nanoscale porous structure is investigated.

High-Resolution Mapping of Local Photoluminescence Properties in CuO/Cu2O Semiconductor Bi-Layers by Using Synchrotron Radiation

The quality of a semiconductor, which strongly affects its performance, can be estimated by its photoluminescence, which closely relates to the defect and impurity energy levels. In light of this, it is necessary to have a measurement method for photoluminescence properties with spatial resolution at the sub-micron or nanoscale. In this study, a mapping method for local photoluminescence properties was developed using a focused synchrotron radiation X-ray beam to evaluate localized photoluminescence in bi-layered semiconductors. CuO/Cu₂O/ZnO semiconductors were prepared on F:SnO₂/soda-lime glass substrates by means of electrodeposition. The synchrotron radiation experiment was conducted at the beamline 20XU in the Japanese synchrotron radiation facility, SPring-8. By mounting the high-sensitivity spectrum analyzer near the edge of the CuO/Cu₂O/ZnO devices, luminescence maps of the semiconductor were obtained with unit sizes of 0.3 μm × 0.3 μm. The devices were scanned in 2D. Light emission 2D maps were created by classifying the obtained spectra based on emission energy already reported by M. Izaki, et al. Band-like structures corresponding to the stacking layers of CuO/Cu₂O/ZnO were visualized. The intensities of emissions at different energies at each position can be associated with localized photovoltaic properties. This result suggests the validity of the method for investigation of localized photoluminescence related to the semiconductor quality.

High-energy x-ray nanotomography introducing an apodization Fresnel zone plate objective lens

In this study, high-energy x-ray nanotomography (nano-computed tomography, nano-CT) based on full-field x-ray microscopy was developed. Fine two-dimensional and three-dimensional (3D) structures with linewidths of 75 nm-100 nm were successfully resolved in the x-ray energy range of 15 keV-37.7 keV. The effective field of view was ∼60 µm, and the typical measurement time for one tomographic scan was 30 min-60 min. The optical system was established at the 250-m-long beamline 20XU of SPring-8 to realize greater than 100× magnification images. An apodization Fresnel zone plate (A-FZP), specifically developed for high-energy x-ray imaging, was used as the objective lens. The design of the A-FZP for high-energy imaging is discussed, and its diffraction efficiency distribution is evaluated. The spatial resolutions of this system at energies of 15 keV, 20 keV, 30 keV, and 37.7 keV were examined using a test object, and the measured values are shown to be in good agreement with theoretical values. High-energy x-ray nano-CT in combination with x-ray micro-CT is applied for 3D multiscale imaging. The entire bodies of bulky samples, ∼1 mm in diameter, were measured with the micro-CT, and the nano-CT was used for nondestructive observation of regions of interest. Examples of multiscale CT measurements involving carbon steel, mouse bones, and a meteorite are discussed.

Recent progress in synchrotron radiation 3D-4D nano-imaging based on X-ray full-field microscopy

The advent of high-flux, high-brilliance synchrotron radiation (SR) has prompted the development of high-resolution X-ray imaging techniques such as full-field microscopy, holography, coherent diffraction imaging and ptychography. These techniques have strong potential to establish non-destructive three- and four-dimensional nano-imaging when combined with computed tomography (CT), called nano-tomography (nano-CT). X-ray nano-CTs based on full-field microscopy are now routinely available and widely used. Here we discuss the current status and some applications of nano-CT using a Fresnel zone plate as an objective. Optical properties of full-field microscopy, such as spatial resolution and off-axis aberration, which determine the effective field of view, are also discussed, especially in relation to 3D tomographic imaging.