Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9496
標題: 藍光可寫一次光碟雙層a-Si/Ni記錄薄膜之研究
A Study of a-Si/Ni Bilayer Recording Film for the Write-once Blue-ray Disk
作者: 簡森村
chien, sen tsun
關鍵字: after
染料層
system
dynamic
訊雜比
非晶矽相
光碟片
吸收率
出版社: 材料工程學研究所
摘要: 一般的可寫一次光碟片(CD-R、DVD-R),多是以有機染料作為記錄層材料,但有機染料對藍光和藍紫光的吸收率偏低,且應用在高記錄密度媒體時,染料層容易塗佈不均,生產時還會造成環境問題。因此,必須發展無機記錄材料來取代傳統的有機染料。 本論文以雙離子束輔助沉積系統(IBAD)製備Si(20nm)/Ni(5nm)雙層記錄薄膜,作為無機可寫一次光碟之記錄材料。由熱分析的實驗結果可知,a-Si/Ni雙層記錄膜在200 oC~350 oC之間會有明顯的反射率變化,當溫度持續的升高至600oC,其反射率便維持一定值不再變化。從GIAD、TEM與AES的分析可得知,反射率發生變化是因為a-Si/Ni雙層記錄膜的Ni與Si原子彼此交互擴散反應,先反應形成NiSi的介穩態相,再由NiSi與Si反應而得到NiSi2,當溫度到達500℃左右便會有結晶矽產生。不過,反射率對溫度的變化關係在500℃附近並沒有反射率的變化,這可能是因為a-Si/Ni之間反應產生NiSi2時,鎳矽化物已將大部分之矽原子耗盡,僅剩下約8.5at%之非結晶矽原子,即使剩下的非晶矽相變化成結晶矽亦無法產生明顯的反射率變化。光學性質分析的結果顯示,初濺鍍a-Si/Ni雙層記錄膜對藍光波長400nm有足夠的吸收率(54.2%)和適當的反射率(38.2%);經600℃熱處理後,吸收率降低到42%,而反射率則增加到57.6%是由於a-Si/Ni雙層記錄膜會形成c- Si與NiSi2的結晶相,可與初濺鍍薄膜產生明顯的光學對比(21.6%),因此,a-Si/Ni雙層記錄膜具有符合藍光可寫一次光碟記錄材料的要求。經由動態測試結果顯示,a-Si/Ni雙層結構膜層在低功率雷射4mW照射下可得到37 dB的訊雜比(CNR),但是並未達到一般光記錄媒體要求的45dB,因此,我們必須進一步修正a-Si/Ni的膜層結構來改善其讀寫特性。
The organic dye has been widely used in write-once disks such as CD-R and DVD-R. However, for use in the write-once blue-ray disk, the absorptance of organic dye at blue wavelength is relatively low, and a uniform organic dye layer is difficult to obtain by spin coating. Besides, the environmental pollution during disk fabrication is another problem. Therefore, we should develop an inorganic recording material to replace the traditional organic recording materials. In this study, a-Si(20nm)/Ni(5nm) bi-layer recording film for the write-once blue-ray disc was prepared by an ion beam assisted deposition system (IBAD). Form the results of thermal analysis, the reflectivity of Si/Ni bi-layer recording film showed an obvious increase at temperatures between 200℃ and 350℃, and then remained constant as the sample was heated form room temperature to 600℃. The results from GIAD, TEM, and AES analyses confirmed that the reflectivity increase corresponded to the formation of metastable NiSi through the diffusion of Ni into the amorphous Si layer, followed by the formation of NiSi2 crystalline phase through the reaction of NiSi with Si. Although the crystallization of remaining amorphous Si was expected at a temperature around 500℃, substantial change of reflectivity was not detected. It is probably because that the formation of NiSi2 has consumed most of the Si atoms and only about 8.5at% of amorphous Si atoms is left to crystallize into crystalline Si that will not lead to an appreciable reflectivity change. At the blue wavelength of 400nm, the as-deposited a-Si/Ni recording film exhibited an absorptance of 54.2% and a reflectivity of 38.2%. After being annealed at 600℃, the absorptance was decreased to 42%, and reflectivity was increased to 57.6% due to the formation of c-Si and NiSi2, resulting in an optical contrast of 21.6%. From the consideration of optical properties, a-Si/ Ni bi-layer is a promising recording material for write-once blue-ray disc. The dynamic test results also demonstrated that CNR of about 37dB can be achieved at laser power of 4mW. Unfortunately, it is still not high enough for practical use in the write-once blue-ray disc. Therefore, we must modify the layer structure of a-Si/Ni to improve the reading and writing ability.
URI: http://hdl.handle.net/11455/9496
Appears in Collections:材料科學與工程學系

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