初始化對DVD-RAM相變化光碟擦拭率影響之研究

Abstract

在多媒體之資料儲存中，相變化光碟是最具潛力的可重複讀寫記錄媒體之一。相變化光碟利用雷射光源能量變化造成記錄層合金材料結晶態與非晶態之相變化而進行讀寫記錄，本實驗以穿透式電子顯微鏡技術對可重複寫入型光碟之記錄層薄膜的相變化過程進行研究。我們首先建立電子顯微鏡試片製作的技術，實驗結果顯示加鍍鐵氣龍薄層於原本光碟的四層薄膜結構中可使反對射層和上介電層後順利地被剝除，而得以對記錄層之微觀結構變化進行觀察。接著我們利用此一試片製作技術對經不同初始化條件的相變化光碟之擦拭率與微觀結構的關係進行研究，實驗結果顯示初始化功率愈高，碟片的擦拭率愈高。初始化次數由1次提高到5次時，擦拭率會提高；由5次提高到100次時，擦拭率變動不大。電子顯微鏡的觀察顯示初始化形成的結晶相帶寬度愈寬時，擦拭率愈高。整體結晶相在雷射讀取範圍內的形貌變化愈小，碟片的擦拭率會愈高，但結晶帶內的殘存粗晶帶愈多時，信號雜訊比愈低。

Phase change optical disk is one of the most promising media for data storage in multimedia era. Phase change optical disk utilizes laser of variable power to induce the amorphous/crystalline phase transition in disk for data recording. In this work we studied the phase change behaviors of active layer in DVD-RAM optical disks by using transmission electron microscopy (TEM). We first established the TEM specimen preparation technique. It was found that the reflective and upper dielectric layers could be easily peeled sway by inserting a tetrafluoroethylene (PTFE) layer into the disks. This enabled us to observe the microstructure change in recording layer of the disks could then be proceeded. The effect of initialization ont the erasability of phase change optical disks was also investigated by applying the established TEM technique. We found the erasability of disks increased with by increase of initialiaztion power. The erasability increased when the initialization cycles was raised from 1 to 5, while on obvious change on erasability was seen when the initialization cycles was increased from 5 to 100. The wider the crystalline band formed during initialization and/or the less the morphology change of crystalline phase covered by incident laser, the higher the disk erasability was observed. The degradation of Carrier to Noise Ratio (CNR) was also observed when coarse grain structure was formed in crystalline band.