Khulbe P K, Xun X, Mansuripur M
Appl Opt. 2000 May 10;39(14):2359-66. doi: 10.1364/ao.39.002359.
We present the results of crystallization and amorphization studies on a thin-film sample of Ge(2)Sb(2.3)Te(5), encapsulated in a quadrilayer stack as in the media of phase-change optical disk data storage. The study was conducted on a two-laser static tester in which one laser, operating in pulsed mode, writes either amorphous marks on a crystalline film or crystalline marks on an amorphous film. The second laser, operating at low power in the cw mode, simultaneously monitors the progress of mark formation in terms of the variations of reflectivity both during the write pulse and in the subsequent cooling period. In addition to investigating some of the expected features associated with crystallization and amorphization, we noted certain curious phenomena during the mark-formation process. For example, at low-power pulsed illumination, which is insufficient to trigger the phase transition, there is a slight change in the reflectivity of the sample. This is believed to be caused by a reversible change in the complex refractive index of the Ge(2)Sb(2.3)Te(5) film in the course of heating above the ambient temperature. We also observed that the mark-formation process may continue for as long as 1 mus beyond the end of the write laser pulse. This effect is especially pronounced during amorphous mark formation under high-power, long-pulse illumination.
我们展示了对封装在四层堆叠结构中的Ge(2)Sb(2.3)Te(5)薄膜样品进行结晶和非晶化研究的结果，该结构与相变光盘数据存储介质中的结构相同。这项研究是在一台双激光静态测试仪上进行的，其中一台激光以脉冲模式工作，在结晶薄膜上写入非晶标记或在非晶薄膜上写入结晶标记。第二台激光以连续波模式低功率运行，在写入脉冲期间和随后的冷却期间，同时根据反射率的变化监测标记形成的过程。除了研究一些与结晶和非晶化相关的预期特征外，我们在标记形成过程中还注意到了某些奇特的现象。例如，在不足以触发相变的低功率脉冲照明下，样品的反射率会有轻微变化。这被认为是由于Ge(2)Sb(2.3)Te(5)薄膜在高于环境温度的加热过程中复折射率的可逆变化引起的。我们还观察到，标记形成过程可能会在写入激光脉冲结束后持续长达1微秒。在高功率、长脉冲照明下形成非晶标记时，这种效应尤为明显。
