Akihiko Saikubo

Effect of Carrier Gas (Ar and He) on the Crystallographic Quality of Networked Nanographite Grown on Si Substrates by Photoemission-Assisted Plasma-Enhanced Chemical Vapor Deposition

In this study, networked nanographite is formed on a Si substrate without any metal catalysts by photoemission-assisted plasma-enhanced chemical vapor deposition. We investigated the carrier gas dependence of the crystallographic quality of networked nanographite when Ar and He are used as the carrier gases. When Ar is the carrier gas, Raman spectroscopy and grazing incident X-ray diffraction show that the crystallographic quality deteriorates makedly with decreasing growth temperature, indicating that amorphous carbon is deposited at low temperatures (below ~500 °C). On the other hand, when He gas is used as a carrier gas, a high quality nanographite can be grown even at temperatures as low as room temperature. Thus, there is a significant difference in the temperature dependence of crystallographic quality for the two carrier gases.

Angle-Dependent Measurement of Near Edge X-ray Absorption Fine Structure of Annealing Effect on Local Structure of Focused-Ion-Beam Chemical Vapor Deposition Diamond-Like Carbon

The annealing effect on the local structure of diamond-like carbon (DLC) formed by Ga+ focused-ion-beam chemical vapor deposition (FIB-CVD) was investigated by the incidence angle-dependent measurement of the C K-edge near edge X-ray absorption fine structure (NEXAFS) from 0 to 60°. The peak intensity corresponding to the resonance transition of 1s →σ* originating from carbon–gallium bonding markedly increased with incidence angle in the spectra of a FIB-CVD DLC film annealed at 400 °C. This angle dependency was attributable to the movement of residual Ga atoms from the bottom to the neighboring surface of the FIB-CVD DLC film.

Scanning Differential-Phase-Contrast Hard X-Ray Microscopy with Wedge Absorber Detector

A new and simple idea for scanning differential-phase-contrast (S-DPC) hard X-ray microscopy has been proposed. It only uses a wedge absorber coupled with two intensity detectors, and is much more sensitive to sample structures than absorption contrast. It can also extract pure quantitative one-dimensional phase gradient given by a sample without an effect of sample absorption. The S-DPC microscope has been constructed at BL24XU of SPring-8, and its feasibility has been successfully demonstrated at the photon energy of 10 keV by clearly visualizing structures of samples. Further, the experimental phase gradient profile agrees well with simulation. By integrating the resultant phase gradient, the corresponding phase shift distribution could be also imaged.

Elementary Analysis of Diamond-Like Carbon Film Formed by Focused-Ion-Beam Chemical Vapor Deposition

This is the first report on the precise elemental composition of a diamond-like carbon (DLC) thin film fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD). The atomic fraction of the FIB-CVD DLC film has been determined to be C:Ga:H=87.4:3.6:9.0 at. % using Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA). The hydrogen content of the FIB-CVD DLC film was lower than that of DLC films formed using other CVD methods.

Effects of Annealing on Material Characteristics of Diamond-Like Carbon Film Formed by Focused-Ion-Beam Chemical Vapor Deposition

The effects of annealing on the material characteristics of a diamond-like carbon (DLC) thin film fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD) were investigated. The elementary analysis, using Rutherford backscattering spectrometry and elastic recoil detection analysis, and measurement of hardness and Youngs modulus, using a nanoindentation technique, were performed on the FIB-CVD DLC thin film by annealing for 1 h in the temperature range from room temperature to 1273 K. Elementary analysis indicated that the Ga content in the FIB-CVD DLC film used as an ion source began to decrease considerably at 523 K and the H content also began to decrease at 773 K. On the other hand, the hardness and Youngs modulus of the FIB-CVD DLC film were found to decrease beyond 773 K. This decrease in hardness is ascribed to the variation in H content rather than in Ga content in the film.

High-Spatial-Resolution Phase Measurement by Micro-Interferometry Using a Hard X-Ray Imaging Microscope

With the aim towards high-spatial-resolution phase measurement, a novel hard X-ray micro-interferometer using an imaging microscope has been proposed and constructed at Hyogo-BL of SPring-8. It is a wavefront-division-type interferometer consisting of a twin zone plate arranged in the same plane. We have succeeded in producing good interference fringes with a visibility of as high as 60% at the photon energy of 9 keV. The fringe scanning method was applied to retrieve phase-shift distribution of a sample. The phase-shift distribution of a 75-µm-thick kapton film and polystyrene microparticles could be imaged clearly with a spatial resolution of 160 nm and the obtained phase shift agreed well with the expected value.

Tandem-Phase Zone-Plate Optics for High-Energy X-ray Focusing

An optical system consisting of two phase zone plates closely arranged in tandem was constructed for focusing high-energy X-rays. The phase zone plates were made from tantalum and their combined thickness was 4.8 µm. An ideal diffraction efficiency of 30% is expected at 30 keV, which is about 3 times higher than that of a single zone plate. The focusing properties at 30 keV were studied both numerically and experimentally. The coaxial tandem arrangement was precisely achieved by observing Youngs interference patterns in the far-field produced by the two point foci. A focus size of ~4 µm was obtained. The photon flux density was 2.2 ×1013 photons/s/mm2, which is 2.4 and 85 times higher than that obtained with a single zone plate and without focusing, respectively. The focused beam was used for scanning X-ray fluorescence microscopy and the residual tin distribution on a float glass surface was imaged.

NEXAFS Study of the Annealing Effect on the Local Structure of FIB‐CVD DLC

Annealing effect on the local structure of diamond like carbon (DLC) formed by focused ion beam‐chemical vapor deposition (FIB‐CVD) was investigated by the measurement of near edge x‐ray absorption fine structure (NEXAFS) and energy dispersive x‐ray (EDX) spectra. Carbon K edge absorption NEXAFS spectrum of FIB‐CVD DLC was measured in the energy range of 275–320 eV. In order to obtain the information on the location of the gallium in the depth direction, incidence angle dependence of NEXAFS spectrum was measured in the incident angle range from 0° to 60°. The peak intensity corresponding to the resonance transition of 1s→σ* originating from carbon‐gallium increased from the FIB‐CVD DLC annealed at 200°C to the FIB‐CVD DLC annealed at 400°C and decreased from that at 400°C to that at 600°C. Especially, the intensity of this peak remarkably enhanced in the NEXAFS spectrum of the FIB‐CVD DLC annealed at 400°C at the incident angle of 60°. On the contrary, the peak intensity corresponding to the resonance tra...