| Summary: | 博士 === 國立交通大學 === 材料科學與工程系所 === 93 === This thesis work studies the methods to enhance the data transfer rate and storage capacity of optical recording media. In the part of data transfer rate enhancement, appropriate amount of nitrogen (N2) doped in the eutectic Sb-Te phase change recording layer is able to accelerate the data transfer rate of optical disks containing Ge-In-Sb-Te (GIST) recoding media. The speed of the amorphous-to-crystalline phase transformation, thermal properties, optical properties and microstructure induced by nitrogen doping in GIST recording layer were investigated and discussed in this work. The experimental results show that for the GIST recording layer doped at the condition of sputtering gas flow ratio of N2/Ar = 3 %, the data transfer rate increases up to 1.5 and 1.6 times as revealed by a static tester containing blue-light laser (λ = 422 nm) and a dynamic tester containing red-light laser (λ = 650 nm). When thin GeNx nucleation promotion layers were further added in below and above the GIST-(N)x recording layer, an overall enhancement up to 3.3 times in data transfer rate was achieved. The nitrogen contents corresponding to various N2/Ar flow ratios (N2/Ar = 0 % ~ 10 %) were calibrated by electron spectroscopy for chemical analysis (ESCA). The changes of thermal, optical and phase constitution of GIST layer resulted from N2 doping were investigated by using differential scanning calorimetry (DSC), ellipsometry, and x-ray diffraction (XRD). These analyses indicated that when appropriate amount of nitrogen was added, the activation energy (Ea) of amorphous-crystalline phase transition of GIST decreased and the optical constants of amorphous and crystalline phases (except the k value of amorphous phase) gradually reduced with the increase of wavelength in the range of 600 to 750 nm. Modulation simulation based on the reflectively of doped GIST layers obtained from static test indicated that appropriate nitrogen doping benefited the signal characteristics of optical disks. Transmission electron microscopy (TEM) revealed that nitrogen doping was able to promote the phase transformation by generating numerous nucleation sites uniformly distributed in the recording layer and hence increased the recrystallization speed.
In the part of storage capacity enhancement of optical disks, we demonstrate a distinct super-resolution phenomenon and signal properties of optical disk with a semiconductor-doped glass (SDG) mask layer containing CdSe nanoparticales. It was found that the 69-nm marks could be consistently retrieved at reading power (Pr) = 4 mW with carrier-to-noise ratio (CNR) = 13.56 dB. The signals were clearly resolved with CNRs nearly equal to 40 dB at Pr = 4 mW when the recorded mark sizes were over 100 nm. The cycleability test indicated that the CdSe-SiO2 SDG layer may serve as a stable and reliable optical mask layer in 105 readout cycles.
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