Hiroshi Miura

Patterning of ZnS–SiO2 by Laser Irradiation and Wet Etching

Generally, ZnS–SiO2 thin film is used as a protective layer in phase-change optical media. The wet etching characteristics of ZnS–SiO2 have been investigated, and it was found that ZnS–SiO2 can be patterned by laser irradiation and wet etching. Convex patterns of ZnS–SiO2 with steep taper profiles were formed. The minimum size of ZnS–SiO2 dots was 90 nm, and the minimum width of ZnS–SiO2 lines was 100 nm. These pattern sizes were approximately one-fourth of the laser beam spot from a 405 nm laser diode (LD) with an objective lens of 0.85 numerical aperture (NA). The pattern edges of ZnS–SiO2 dots and lines were clear and smooth. These results prove that ZnS–SiO2 is a useful material for forming nanometer-scale patterns.

In-Sb Phase-Change Material for 16× Rewritable Digital Versatile Disk

We investigated Sb-based In-Sb as a material for high-speed recording that is capable of maintaining a highly stable amorphous phase. The crystalline phase of In-Sb is unstable at approximately its eutectic composition. After an aging test, InSb was segregated, and its reflectivity was reduced. For an Sb-rich In-Sb, we confirmed that its crystalline phase is stable and its crystallization speed is high. We demonstrated the feasibility of 16× digital versatile disk (DVD) recording using 2T-period multiple-pulse strategy.

Amorphous SiOx:H alloy films as wide optical-gap materials

Abstract Hydrogenated a-SiO x :H films are prepared by the r.f. glow-discharge decomposition of a SiH 4 and CO 2 gas mixture. The optical and electrical properties of these films are discussed in connection with their oxygen content. A photo-diode with a double-layer structure consisting of glass/ITO/a-SiO x :H/a-Si:H/Al is discussed.

Decision Feedback Partial Response Maximum Likelihood for Super-Resolution Media

A decision feedback partial response maximum likelihood (PRML) for super-resolution media was developed. Decision feedback is used to compensate for nonlinear distortion in the readout signals of super-resolution media, making it possible to compensate for long-bit nonlinear distortion in small circuits. An field programmable gate array (FPGA) was fabricated with a decision feedback PRML, and a real-time bit error rate (bER) measuring system was developed. As a result, a bER of 4×10-5 was achieved with an actual readout signal at the double density of a Blu-ray disc converted to the optical properties of the experimental setup using a red-laser system. Also, a bER of 1.5×10-5 was achieved at double the density of an a high definition digital versatile disc read-only memory (HD DVD-ROM), and the radial and tangential tilt margins were measured in a blue-laser system.

Effect of Electron Beam Irradiation on Si Surface Cleaning in Ultrahigh-Vacuum System

Effect of electron beam irradiation (15 kV) on Si surface cleaning prior to epitaxial growth in an ultrahigh-vacuum system was investigated. A CaF2 film was epitaxially grown on the Si surface, and the interface was observed by high-voltage electron microscopy. Amorphous layers, which were observed in the interface prepared with conventional thermal treatment at 750°C, became much smaller with electron beam irradiation after the thermal treatment. Based on the electron microscope observation, the effect of electron beam irradiation on Si surface cleaning was briefly discussed.

ZnInS Thin Film Solar Cell Fabricated by Sputtering Process

To achieve low cost solar cells, new fabrication processes should be developed for higher throughput and utilization rate. In this study, we focused on a sputtering method and found that a multinary compound ZnInS (II–III–VI) is suitable for this process. The ZnInS thin film deposited by sputtering had an n-type semiconductor characteristic. A AgInTe/ZnInS thin-film solar cell fabricated by the sputtering process in a layer structure of glass/Mo/AgInTe/ZnInS/AZO showed a conversion efficiency of over 1%, the origin of which was mainly the ZnInS layer. These results suggested that ZnInS is a strong candidate photovoltaic material for fabrication with the sputtering process.

Structure Analysis of ZnS-SiO2 Thin Film and Patterning by Heat-Mode Lithography

A tetrahedral network structure like ZnS crystal is found to exist in the amorphous ZnS-SiO2 thin film. It is considered that the etching selectivity in as-deposited and annealed ZnS-SiO2 thin film becomes large due to the growth of ZnS crystals by annealing. There is optimum mixture rate of ZnS for patterning of Zns-SiO2 thin film by the heat-mode lithography, and the ZnS-SiO2 dots with clear and smooth edges were formed with increasing in the ZnS mixture rate to 80%