Study of the microstructures and optical properties of Ge based write-once optical disc media
Date Issued
2007
Date
2007
Author(s)
Wu, Ting-Hau
DOI
zh-TW
Abstract
At present, write-once optical disc is made of organic dye. However, uniformity and environmental pollution issues are difficult to be reduced for the high density recording disc. Hence, ionrganic recording materials were proposed to replace the organic materials. In this study, metal induced crystallization (MIC) mechanism for alloy and bilayer structure of inorganic recording thin films were investigated. Four kinds of recording media, Ge100-XCuX, Ge/Al, Ge/Au and Ge/PCM thin film were studied. Thermal analysis shows that the phase-transition temperatures of the Ge100-XCuX, Ge/Al, Ge/Au film is 310~320 ℃, 275℃~285 ℃, 190 ℃~200 ℃and 130 ℃~140 ℃, respectively. The X-ray diffraction analysis reveals that the as-deposited Ge100-XCuX film is a supersaturated ε-Cu3Ge single phase structure. It becomes Ge and ε-Cu3Ge two phases structure after post-annealed at 400 ℃ for 30min. The as-deposited Ge/Al bilayer film is amorphous structure. It becomes Ge3Al5 (004) phase structure after post-annealed at 280 ℃ for 30min, The TEM analysis shows that after annealing at 400 ℃ for 30min, the Ge grain segregate in the Ge100-XCuX matrix, and the film was transformed to ε-Cu3Ge and Ge phases, Ge3Al5 was found in as-deposited Ge/Al films, after 280 ℃, 30mins annealing, it will transform to Ge(111), Al(111), and Ge3Al5. As-deposited Ge/Au bilayer had by Ge2Au3 and Au crystal phase. Ge2Au3 interface was founed by cross-sectional TEM image, after 220 ℃, 30 min annealing. Inter-diffusion of Au atoms into Ge layer formed a Ge2Au3 (3 2 1) metastable phase with d-spacing 3.20 Å, when the annealing temperature was further increased to 320 ℃, closed packed plane of Ge (1 1 1) with d-spacing 3.26 Å would segregate out of the meatastable Ge2Au3 phase. The Ge/PCM bilayer was amorphous at as-deposited state. After continuous annealing from room temperature, it has 2 phase change temperature at 130~140 ℃ and 500~520 ℃, respectively. The phase change temperature at 130~140 ℃ was owing to the phase change of InSbTe layer and few amount of Ge Crystallites. As the annealing temperature is further increased to 520 ℃, which is closed to the crystallization temperature of pure Ge, the InSbTe layer and Ge layer start to inter-diffusion to each other. In this step, it will form Ge1Sb2Te4 (009) or 4 elements alloy compound, which is different from the MIC mechanism of Ge/Metal bilayer structure.
The dynamic tests show that jitter value of Ge/Al was 6.3% under 12X FVD formation; PRSNR, SbER and modulation of Ge/Au bilayer under 1~2X HD DVD formation are 21.3 dB, 3*10-8 and 0.76, respectively. On the other hand, the jitter value of Ge/PCM was 7.9% under 8X DVD formation, and the DOW experiment indicated that the jitter value of Ge/InSbTe was 13.5% and 18% after second and third direct over write.
Subjects
鍺
無機
可寫一次
記錄媒體
Ge
inorganic
write once
recording media
SDGs
Type
thesis
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