Zhang Bin, Wang Xue-Peng, Shen Zhen-Ju, Li Xian-Bin, Wang Chuan-Shou, Chen Yong-Jin, Li Ji-Xue, Zhang Jin-Xing, Zhang Ze, Zhang Sheng-Bai, Han Xiao-Dong
Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China.
Sci Rep. 2016 May 3;6:25453. doi: 10.1038/srep25453.
Ge-Sb-Te alloys have been widely used in optical/electrical memory storage. Because of the extremely fast crystalline-amorphous transition, they are also expected to play a vital role in next generation nonvolatile microelectronic memory devices. However, the distribution and structural properties of vacancies have been one of the key issues in determining the speed of melting (or amorphization), phase-stability, and heat-dissipation of rock-salt GeSbTe, which is crucial for its technological breakthrough in memory devices. Using spherical aberration-aberration corrected scanning transmission electron microscopy and atomic scale energy-dispersive X-ray mapping, we observe a new rock-salt structure with high-degree vacancy ordering (or layered-like ordering) at an elevated temperature, which is a result of phase transition from the rock-salt phase with randomly distributed vacancies. First-principles calculations reveal that the phase transition is an energetically favored process. Moreover, molecular dynamics studies suggest that the melting of the cubic rock-salt phases is initiated at the vacancies, which propagate to nearby regions. The observation of multi-rock-salt phases suggests another route for multi-level data storage using GeSbTe.
锗锑碲合金已广泛应用于光/电存储领域。由于其极快的晶态-非晶态转变速度，它们也有望在下一代非易失性微电子存储器件中发挥至关重要的作用。然而，空位的分布和结构性质一直是决定岩盐结构的锗锑碲的熔化（或非晶化）速度、相稳定性和散热性的关键问题之一，而这对于其在存储器件中的技术突破至关重要。利用球差校正扫描透射电子显微镜和原子尺度能量色散X射线映射，我们观察到一种新的岩盐结构，在高温下具有高度的空位有序排列（或层状有序排列），这是由具有随机分布空位的岩盐相发生相变导致的。第一性原理计算表明，这种相变是一个能量有利的过程。此外，分子动力学研究表明，立方岩盐相的熔化始于空位，并传播到附近区域。多岩盐相的观察为利用锗锑碲进行多级数据存储提供了另一条途径。
