Papers by Author: Hiroshi Masumoto

Abstract: The large scale SSPS (Space Solar Power System) needs large reflection mirrors for sunlight concentration. To use film mirror in space, the mirror must have lightweight structures and resistive to harsh space environment. The wavelength selective filter to avoid heat is a dielectric multilayer film which has FGM structure. In this article, we will report the development of a lightweight wavelength selective mirror and wavelength selection on the solar light excitation laser.

Abstract: The surface oxide films were prepared by Electron Cyclotron Resonance (ECR) plasma oxidation on Ti substrates. Octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) peaks were formed after calcification by supersaturated calcium and phosphate solutions. Calcification ability was enhanced with increasing the oxidation time and the total pressure of ECR plasma treatment during oxidation. The results demonstrated that the calcium phosphate nucleation and the deposition can be controlled by various ECR plasma conditions.

Abstract: Surface titanium oxide (TiO2) films were fabricated on implant titanium (Ti) at low temperatures by electron-cyclotron-resonance (ECR) plasma oxidation. The relationship among the oxidization conditions, crystal structure, morphology and osteoconductive property were investigated. Although crystallized TiO2 film was not prepared by thermal oxidation at 300°C, crystallized rutile-type TiO2 film was formed by ECR plasma oxidation at 300°C. Rough morphology was observed in the substrate surface oxidized by ECR plasma. Mixtures of octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) were observed after calcification. The XRD peak intensities of the OCP and DCPD formed on the ECR plasma oxidized Ti were larger than those of calcified on the thermal oxidized Ti. ECR plasma oxidation at low temperature would induce osteoconductive calcium phosphate on implant Ti.

Abstract: Epitaxial BaRuO3 (BRO) and CaRuO3 (CRO) thin films were prepared on (001), (110) and (111) SrTiO3 (STO) single-crystal substrates by laser ablation, and their microstructures and anisotropy of electrical conductivity were investigated. The (205) (104), (110) and (009) oriented BRO thin films, and (001), (110) and (110) oriented CRO thin films were grown epitaxially on (001), (110) and (111) STO substrates with in-plain orientation, respectively. The (009) BRO thin film and (001) CRO thin film has a flat surface result from a good lattice matching to STO substrates. The (205) (104) BRO thin film and (111) CRO thin film exhibited orthogonal- and hexagonal-shaped texture, respectively. The (110) BRO thin film and (110) CRO thin film showed an island growth due to (110) surface feature of cubic perovskite structure. Epitaxial BRO and CRO thin films have a high electrical conductivity with a metallic conduction, the (111) CRO thin films exhibited the highest conductivity of 1.4×105 S·m-1.

Abstract: Au/SiO2 nano-composite multilayer thin films with different thickness were prepared on a quartz substrate by magnetron plasma sputtering. The microstructure, morphology and optical properties of the films were investigated by using TEM and optical absorption spectra. [Au/SiO2]×5 and [Au/SiO2] × 11 multilayer thin films have well-defined interface. The thickness of the multilayer was 60nm and 130 nm for the thin films with 5 and 11 layers, respectively. The optical absorption peaks due to the surface plasma resonance appeared at a wavelength of 560 nm for the both [Au/SiO2]×5 and [Au/SiO2]×11 thin films. The intensity of the absorption peak increased with increasing numbers of deposition layers. The optical absorption spectra of Au/SiO2 multilayer thin films are well agreement with the theoretical optical absorption spectra calculated from rewritten Maxwell–Garnett effective medium theory.

Abstract: BaRuO3(BRO) and BaIrO3(BIO) thin films were prepared by laser ablation, and the effects of preparation conditions on the structure, morphology and electrical conductivity were investigated. BRO thin films deposited at oxygen partial pressure (PO2) = 13 Pa and substrate temperature (Tsub) < 573 K were amorphous. At Tsub = 573 K, the rhombohedral BRO thin films with (110) orientation were obtained. BRO thin films prepared at Tsub = 773 K and PO2= 13 Pa exhibited the resistivity of 5x10-6
m and showed metallic conduction. BIO thin films deposited at PO2= 40 Pa and Tsub < 623 K were amorphous. Tsub > 623 K, the BIO thin films crystallized into a 6H structure were obtained. The resistivity of the BIO films at PO2= 40 Pa decreased from 1.4x10-2 to 4x10-4
m with decreasing Tsub from 1073 to 573 K.

Abstract: Titania (TiO2) thin films were fabricated on titanium (Ti) substrates at low temperatures by electron cyclotron resonance (ECR) plasma oxidation, and the relationship among the oxidization conditions, crystal structure and osteoconductive property was investigated. Amorphous TiO2 films were obtained below 300°C and crystallized rutile-type TiO2 films were obtained above 400°C. The XRD peak intensity of rutile TiO2 increased with increasing oxidation temperature. Mixtures of octacalcium phosphate (OCP) and Dicalcium phosphate dihydrate (DCPD) peaks were observed after calcification. The intensity of the OCP and DCPD peaks after calcification increased with increasing oxidation temperature. The ECR plasma was significantly effective to prepare crystallized TiO2 films at low temperatures.

Abstract: Au/SiO2 nano-composite thin films with 3 to 65 vol% Au content were prepared by induction-coil-coupled plasma sputtering. Au particles dispersed in the SiO2 matrix can be prepared by controlling the deposition time of one Au layer and the thickness of the one SiO2 layer. The Au nano-particle dispersed Au/SiO2 multilayer with an uniform nano-layered microstructure showed the absorption peak at the wavelength of 560 nm. The heat-treated Au/SiO2 films containing 3 to 65 vol% Au showed absorption peaks at the wavelength of 540 to 560 nm, while no absorption peak was observed in the as-deposited multilayers containing more than 12 vol% Au.

Abstract: SrRuO3 (SRO) thin films were prepared by laser ablation. The optimum preparation condition of highly electrically conductive SRO thin films was investigated. The substrate temperature (Tsub) was changed from room temperature to 973 K, and the deposition atmosphere was at a high vacuum (P = 10-6 Pa) and in O2 at oxygen pressures (PO2) of 0.13 and 13 Pa. The films deposited at P = 10-6 Pa and PO2 = 0.13 Pa were amorphous structure. At Tsub > 573 K and PO2 = 13 Pa, well-crystallized pseudo-cubic SRO thin films with (110) orientation were obtained. With increasing Tsub, the conductivity of SRO films increased from 7.7×103 to 9.1×104 S·m-1. The epitaxially grown SRO films on (100) SrTiO3 substrates exhibited the highest conductivity of 1.8×105 S·m-1.