| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 91 === In rewritable phase-change optical recording media, the data are recorded based on amorphization and crystallization of the phase change material. Information can be read out as change in reflectance. Stoichiometric compound alloy materials, which have fast crystallization rate, were the most popular phase-change recording medium to date. Another chalcogenide material, InTe eutectic alloy, was considered to have a great potential to be a better phase-change optical recording media because that Te-based alloy has easy amorphization, suitable optical characteristics and the sufficiently low melting point.
In the present study, In2Te3 alloy film was prepared by vacuum co-deposition, following by a heat-treatment at N2 atmosphere and the scanning of a diode laser. The XRD results show that the phase of In2Te3 alloy film changes from amorphous state to crystalline state after heat-treatment. Furthermore, different crystalline orientations were observed after heat-treatment at different temperature, and SEM images prove the presence of crystalline morphology of In2Te3 film after heat-treatment. From the OM images and SEM images, one observed that after the In2Te3 film scanned by a diode laser, there are morphology changes, surface melting or/and flow of the molten film. A wilder and deeper melt zone of film is observed when the film was scanned by a laser at higher power or lower speed .The complex refractive indices and reflectivity of amorphous and crystalline recording films were measured. The crystallization temperature of In2Te3 alloy material is measured by DSC, and is determined to be about 225℃. The crystallization temperature is sufficiently high for thermal stablility.
The finite element method was applied to solve for the 3 dimensional temperature profile of the disc. The results indicate that data can be recorded on the disc at very high scanning speed either in CD system(λ=780nm)or DVD system(λ=640nm). The recorded-mark size as well as peak temperature of recording film were proportional to laser power, but inversely proportional to scanning speed, the heating rate and the cooling rate was proportional to scanning speed. The recorded-mark size was proportional to the parameter group (P1Vx-0.25).
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