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Diffusion-assisted displacive transformation in Yttrium-doped Sb2Te3 phase change materials
Acta Materialia ( IF 9.4 ) Pub Date : 2023-03-01 , DOI: 10.1016/j.actamat.2023.118809
Kaiqi Li, Bin Liu, Jian Zhou, Stephen R. Elliott, Zhimei Sun

Phase transformations between cubic and rhombohedral states of phase-change chalcogenide materials have been considered to result in small resistance drift, fast read/write speeds, and low power consumption in phase-change memory devices. However, it is difficult to observe such dynamic processes by experiments. Especially, the ultra-fast speed of, and ultra-small area affected during, the displacive transformation involved in the phase transformations, lead to a lack of direct evidence for studying the transformation mechanism. Here, we directly observed the reversible displacive transformations in Yttrium-doped Sb2Te3 (Y-Sb2Te3) by ab initio molecular-dynamics (AIMD) simulations. The forward displacive transformation, from the cubic to the rhombohedral phase, can be spontaneously realized through a two-step transformation, the shearing, and contraction between Te-Sb-Te-Sb-Te building blocks. On the other hand, the backward transformation, from the rhombohedral to the cubic phase, requires high-temperature heating (above 900 K) and atomic diffusion. The diffusion of cation-site Sb atoms into interstitial sites, located in the interlayers of building blocks, triggers the backward transformation; thus, it is diffusion-assisted. Moreover, the enhancement of thermostability of the cubic phase by Y dopants promotes the backward transformation. This study can improve the understanding of the displacive transformations in phase-change materials and may offer new insights into developing phase-change memory devices based on Sb2Te3.



中文翻译:

掺钇 Sb2Te3 相变材料中的扩散辅助位移转变

相变硫族化物材料的立方和菱面体状态之间的相变被认为可以导致相变存储器件的电阻漂移小、读/写速度快和功耗低。然而,很难通过实验观察这样的动态过程。尤其是相变所涉及的位移转变速度超快、影响范围极小,导致转变机理研究缺乏直接证据。在这里,我们从头开始直接观察了掺钇 Sb 2 Te 3 (Y-Sb 2 Te 3 )中的可逆位移转变分子动力学 (AIMD) 模拟。从立方相到菱面体相的正向位移转变可以通过两步转变、Te-Sb-Te-Sb-Te 结构单元之间的剪切和收缩自发实现。另一方面,从菱面体相到立方相的反向转变需要高温加热(900 K 以上)和原子扩散。阳离子位置的 Sb 原子扩散到位于结构单元层间的间隙位置,触发了反向转换;因此,它是扩散辅助的。此外,Y掺杂对立方相热稳定性的增强促进了向后转变。23

更新日期:2023-03-05
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