Ichiro Hirosawa

The Advanced Automation for Powder Diffraction toward Industrial Application

A highly automated system for powder diffraction with synchrotron radiation was installed on the large Debye‐Scherrer camera at the BL19B2 Engineering Science Research I beamline of SPring‐8. Combined with a sample transfer and an automated centering system, we have succeeded in increasing the ratio of exposure time in the user beam time to 85%. The proposed system can be applied to a wide range of industrial uses.

Site of Doped Eu in BaMgAl 10 O 17 Studied by X-Ray Absorption Fine Structure

The sites that doped divalent Eu ions occupy in BaMgAl 10 O 17 were studied by X-ray absorption fine structure (XAFS) measurement. The radial structural function and the Fourier-filtered EX-AFS wiggle derived from the observed XAFS spectrum suggested that Eu ions occupy the Beevers-Ross and/or anti-Beevers-Ross sites. Observed XANES spectrum also could be explained by Beevers-Ross site occupation.

Evaluation of Properties of SiO2 Films Fabricated by Plasma Oxidation

Properties of SiO2 films formed by plasma oxidation were compared with those of films formed by thermal oxidation. X-ray reflectivity (XRR) was used to evaluate the SiO2/Si interface roughness, thickness, and density of SiO2 films. Chemical properties of the SiO2 films were investigated by X-ray photoelectron spectroscopy (XPS). Moreover, the relation between film density and its chemical properties was evaluated. This evaluation shows that SiO2 films fabricated by plasma oxidation have higher density and a smoother interface than those fabricated by thermal oxidation. In addition, oxidation rate was increased and interface quality and density were improved by incorporating hydrogen in the plasma atmosphere.

Improvement in Stability of SPring‐8 Standard X‐Ray Monochromators with Water‐Cooled Crystals

SPring‐8 standard double‐crystal monochromators containing water‐cooled crystals were stabilized to a sufficient level to function as a part of optics components to supply stable microfocused x‐ray beams, by determining causes of the instability and then removing them. The instability was caused by two factors—thermal deformation of fine stepper stages in the monochromator, which resulted in reduction in beam intensity with time, and vibrations of coolant supply units and vacuum pumps, which resulted in fluctuation in beam intensity. We remodeled the crystal holders to maintain the stage temperatures constant with water, attached x‐ray and electron shields to the stages in order to prevent their warming up, introduced accumulators in the water circuits to absorb pressure pulsation, used polyurethane tubes to stabilize water flow, and placed rubber cushions un der scroll vacuum pumps. As a result, the intensity reduction rate of the beam decreased from 26% to 1% per hour and the intensity fluctuation from 13% to 1%. The monochromators were also modified to prevent radiation damage to the crystals, materials used as a water seal, and motor cables.

Structural Phase Transition of J-Aggregate Crystallites on the Binary Counter-Ion Subphase

The recently found chromic phase transition of merocyanine J-aggregates monolayer on the aqueous subphase containing Cd 2 + and Mg 2 + was investigated by the grazing-incidence X-ray diffraction method. The evidence of the structural difference between the phases of J-band at 620 nm and 590 nm was obtained by the investigations on the monolayers prepared at the different molar ratios of Cd 2 + and Mg 2 + . The change in a Braggs peak was observed at the ratio of the ions, where the J-band wavelength also exhibited the discrete shift. The relationship between the obtained results and the phase diagram determined by the shift of the J-band wavelength was also discussed from the viewpoint of the formation mechanism of J-aggregate crystallites.

Structural Phase Transition in Two-Dimensional Crystallites of Organic Dye Molecules Formed on Aqueous Subphases

The 2D crystallites of polar organic dye molecules on an aqueous subphase exhibit a thermochromic phase transition. The visible absorption band of the crystallites depends on the temperature and the composition of the subphase. In-situ observations of the phase transition were carried out by a grazing incidence X-ray diffraction method. A shift and a split of the diffraction peaks were observed between the different phases, indicating a change in the molecular arrangement of the crystallites in their chromic transition.

Study of 2D phase transition of polar organic dye molecules at the air-water interface by using granzing-incidence X-ray diffraction

The grazing incidence X-ray diffraction from the 2D polar crystallites of organic dye molecules on an aqueous subphase was measured. The structure of the 2D crystallites shows a dependence on the subphase composition, and this dependence corresponds well to the results obtained from Langmuir-Blodgett films, which consist of the multilayer of the 2D crystallites deposited on the solid planar supports.

Characterization of Amorphous High-k Thin Films by EXAFS and GIXS

Silicon and nitrogen incorporated Hf oxide (HfSiON) is considered to be a promising alternative gate insulator for next‐generation MOSFETs. EXAFS and GIXS (Grazing Incidence X‐ray Scattering) have been applied to the characterization of amorphous HfSiON films at SPring‐8. Novel cluster models have been suggested based on the analogy to the ordered states for the Zr‐O‐N ternary system.