title: Vacancy Structures and Melting Behavior in Rock-Salt GeSbTe.
abstract: 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.
authors.affiliation: Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China.
authors.forename: Xue-Peng
authors.initials: XP
authors.lastname: Wang
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Zhen-Ju
authors.initials: ZJ
authors.lastname: Shen
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China.
authors.forename: Xian-Bin
authors.initials: XB
authors.lastname: Li
authors.affiliation: Department of Physics, Beijing Normal University, Beijing 100875, China.
authors.forename: Chuan-Shou
authors.initials: CS
authors.lastname: Wang
authors.affiliation: Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.
authors.forename: Yong-Jin
authors.initials: YJ
authors.lastname: Chen
authors.affiliation: Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Ji-Xue
authors.initials: JX
authors.lastname: Li
authors.affiliation: Department of Physics, Beijing Normal University, Beijing 100875, China.
authors.forename: Jin-Xing
authors.initials: JX
authors.lastname: Zhang
authors.affiliation: Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.|Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China.|Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Sheng-Bai
authors.initials: SB
authors.lastname: Zhang
authors.affiliation: Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Han