Vacancy or not: An insight on the intrinsic vacancies in rocksalt-structured GeSbTe alloys from ab initio calculations

¹ Department of Materials Science and Engineering, College of Materials, Xiamen University 361005 Xiamen, China
² Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen University 361005 Xiamen, China
³ State Key Laboratory of Functional Materials for Informatics, Laboratory of Nanotechnology, Shanghai Institute of Micro-System and Information Technology, Chinese Academy of Sciences - 200050 Shanghai, China
⁴ Department of Physics and Astronomy, Condensed Matter Theory Group - Box 520, 75120 Uppsala, Sweden

^a zmsun@xmu.edu.cn

Received: 26 April 2011
Accepted: 26 May 2011

Abstract

Rocksalt-structured GeSbTe (GST) phase-change materials contain significant amounts of intrinsic vacancies at one sublattice. On the basis of ab initio total energy calculations, we have shown that the so-called intrinsic vacancies result from geometrical voids that originate from packing spaces for lone pairs of electrons tightly bound to specific Te layers where a weak bonding exists. The existence of such geometrical voids is concomitant with a narrow band gap. The present results will shed new insights on the intrinsic vacancies in rocksalt-structured GST.