Structural role of vacancies in the phase transition of Ge2Sb2Te5 memory materials
Structural role of vacancies in the phase transition of Ge2Sb2Te5 memory materials
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DOI：
10.1103/physrevb.84.094124
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发表时间：
2011-09-27
影响因子：
3.7
通讯作者：
Elliott, S. R.
中科院分区：
文献类型：
--
作者：
Lee, T. H.;Elliott, S. R.
非晶态材料中的晶化需要大量的原子扩散才能发生结构有序化。空位可以在晶化过程中发挥关键作用，尽管人们对相变材料知之甚少。本文利用从头算分子动力学模拟方法，观察了Ge_2Sb_2Te_5(GST)材料中空位的演化及其对晶化过程的影响。研究发现，空位多以Te原子为邻位。非晶相中的Ge/Sb原子扩散到晶体-玻璃界面的空位有助于形成稳定的立方团簇，这些团簇有可能作为晶核生长。这种具有特殊再分布的选择性空位扩散促进了晶体成核过程，从而显著促进了该材料的快速晶化。
Crystallization in amorphous materials requires significant atomic diffusion for structural ordering to occur. Vacancies can play a critical role during the crystallization process, although little is known for phase-change materials. Here, using ab initio molecular-dynamics simulations, we have observed how vacancies evolve and influence the crystallization process in Ge2Sb2Te5 (GST) materials. It was found that vacant sites have mostly Te atoms as neighbors. The diffusion of Ge/Sb atoms in the amorphous phase to vacancies at the crystal-glass interface helps in the formation of stable cubic clusters that potentially grow as nuclei for crystallization. Such selective vacancy diffusion with its particular redistribution facilitates the crystal-nucleation process, thereby significantly contributing to the fast speed of crystallization in this material.