Yoshiyuki Yokoyama

10 keV X-Ray Phase-Contrast Microscopy for Observing Transparent Specimens

Hard X-ray phase-contrast microscopy has been performed with phase plates of tantalum using an X-ray beam from an undulator in SPring-8. The photon energy was set at 10 keV near the L3 absorption edge of tantalum (9.9 keV) in order to increase the phase contrast. To demonstrate its capability, a transparent specimen was imaged clearly in the reverse contrast with phase plates to shift the phase by one-quarter and three-quarters of a period, while conventional absorption imaging showed little contrast. Further, an image contrast as high as approximately 40% can be obtained for the cell walls of another specimen.

X-ray phase-contrast imaging with submicron resolution by using extremely asymmetric Bragg diffractions

We have obtained x-ray phase-contrast images with high spatial resolution by using extremely asymmetric Si 111 Bragg diffractions near the critical angle of the total reflection. The x-rayimage could be magnified to 294 times in both vertical and horizontal directions. By using this x-ray microscopy system, we have observed clear phase-contrast images of a 0.7-μm-wide gold-line pattern.

High-resolution hard X-ray phase-contrast microscopy with a large-diameter and high-numerical-aperture zone plate

An imaging transmission hard X-ray microscope has been constructed at beamline BL24XU of SPring-8. It makes use of a phase zone plate made of tantalum with a diameter of 1 mm and an outer-most zone width of 50 nm, aiming at a wide field of view and a high spatial resolution. The performance test was carried out at a photon energy of 10 keV. A field of view as wide as approximately 200 microm in diameter was achieved. The spatial resolution was measured to be 220 nm by analyzing a knife-edge image. Further, a line-and-space pattern as fine as 100 nm could be imaged. By placing a phase plate made of gold in the back focal plane of the zone plate, phase-contrast microscopy using Zernikes method was also carried out. The feasibility of phase-contrast microscopy for observing transparent samples was successfully demonstrated by imaging small polystyrene particles.

Nanoparticle free polymer blends for light scattering films in liquid crystal displays

This paper reports an approach using nanoparticle free polymer blends for light scattering films in liquid crystal displays. The ability to create the regularly structured circle of approximately 200 nm diameter in the light scattering film by blending two specified polymers with carboxylic acid groups and epoxy groups was demonstrated. The developed light scattering film based on thermosetting system indicated regularly structured nanomorphology, high light scattering rates of more than 3.9% at 300–600 nm of wavelength, and fast thermal cross-linking reaction at 150 °C and 60 s in thermosetting conditions for high productivity.

500-nm-Resolution 10 keV X-Ray Imaging Transmission Microscope with Tantalum Phase Zone Plates

An imaging transmission hard X-ray microscope has been constructed at the Hyogo-BL (BL24XU) of SPring-8. It makes use of X-ray phase zone plates (PZPs) made of tantalum as its condenser and objective lenses. The objective PZP has an outermost zone width of 250 nm, which corresponds to the theoretically expected spatial resolution of 300 nm. An experiment was performed at the photon energy of 10 keV to check the performance of the microscope. Since a 250 nm line-and-space pattern was clearly resolved, we concluded that the microscope attained a spatial resolution limit better than 500 nm. A few samples were also examined and the feasibility of the microscope was successfully demonstrated.

Measurement of Strain Distribution in InGaAsP Selective-Area Growth Layers Using a Micro-Area X-Ray Diffraction Method with Sub-µm Spatial Resolution

We developed a micro-area X-ray diffraction system using a sub-µm X-ray beam of 10 keV energy that was produced by a phase zone plate made of tantalum. Using this system, we were able to measure the lattice strain distribution in InGaAsP metalorganic vapor phase epitaxial layers selectively grown on InP stripe regions a few µm in width between a pair of SiO2 mask stripes, with strain sensitivity of about 1×10-4. We found that the strain distribution in a 3-µm-wide stripe layer is almost completely uniform, while that in a 4-µm-wide layer is not.

Development of light-scattering thermal cross-linking package film based on self-assembly for liquid crystal display using light emitting diode

We present investigations of light-scattering thermal cross-link package film based on self-assembly for liquid crystal display using light emitting diode. Thermal cross-link package films based on selfassembly indicated good nano regularly-structured patterning for light-scattering, excellent environmental stability of optical parameters, and solvent intermixing resistance after thermal cross-link reaction. The developed light-scattering thermal cross-link package film-s based on self-assembly is one of the most promising processes ready to be incorporated into the mass production of patterning light-scattering optical layer for advanced liquid crystal display, organic electroluminescent display, and solar cell devices.

230 nm Resolution 10 keV X-Ray Imaging Transmission Microscope with Parallel Beam Illumination

The spatial resolution of an imaging transmission hard X-ray microscope has been greatly enhanced by the use of an X-ray phase zone plate with a numerical aperture five times larger than the previous one [Y. Kagoshima, T. Ibuki, K. Takai, Y. Yokoyama, N. Miyamoto, Y. Tsusaka and J. Matsui: Jpn. J. Appl. Phys. 39 (2000) L433]. An experiment was carried out at the photon energy of 10 keV to evaluate the performance of the microscope. It was confirmed that the spatial resolution was 230 nm and that a line-and-space pattern as fine as 100 nm could be imaged.