Understanding the phase-change mechanism of rewritable optical media
Understanding the phase-change mechanism of rewritable optical media
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DOI：
10.1038/nmat1215
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发表时间：
2004-10-01
期刊：
影响因子：
41.2
通讯作者：
Uruga, T
中科院分区：
文献类型：
--
作者：
Kolobov, AV;Fons, P;Uruga, T
当今的多媒体强烈依赖可重写相变光学存储器。我们证明，与目前的共识不同，DVD-RAM 中选择的材料 Ge2Sb2Te5 不具有岩盐结构，但更可能由明确定义的刚性构件组成，这些构件在空间中随机定向，符合立方对称性。激光诱导的非晶化导致共价键的急剧缩短和均方相对位移的降低，表明短程有序程度的大幅增加，这与典型共价键固体的非晶化形成鲜明对比。这种新颖的有序-无序转变是由于Ge原子从八面体位置伞形翻转到四面体位置而没有强共价键的断裂。正是这种独特的两种状态转换性质确保了 DVD 的快速性能和超过一千万个周期的可重复切换。
Present-day multimedia strongly rely on rewritable phase-change optical memories. We demonstrate that, different from the current consensus, Ge2Sb2Te5, the material of choice in DVD-RAM, does not possess the rocksalt structure but more likely consists of well-defined rigid building blocks that are randomly oriented in space consistent with cubic symmetry. Laser-induced amorphization results in drastic shortening of covalent bonds and a decrease in the mean-square relative displacement, demonstrating a substantial increase in the degree of short-range ordering, in sharp contrast to the amorphization of typical covalently bonded solids. This novel order-disorder transition is due to an umbrella-flip of Ge atoms from an octahedral position into a tetrahedral position without rupture of strong covalent bonds. It is this unique two-state nature of the transformation that ensures fast DVD performance and repeatable switching over ten million cycles.