Vacancy-mediated electronic localization and phase transition in cubic Sb2Te3

Abstract Sb2Te3 is a very promising phase-change material due to its fast reversible phase transition between the amorphous and crystal phases. Crystalline Sb2Te3 can adopt the cubic (rock-salt) or rhombohedral structure, and for the cubic Sb2Te3 which is metastable, 33.3% vacancies exist in the Sb sublattice. The intrinsic vacancies which normally have significant effects on the fundamental property of the phase-change material need to be thoroughly studied for the practical application of Sb2Te3. In this work, by using ab initio calculations, various configurations of the vacancies with different randomness as well as their effects on the electronic property and phase transition of cubic Sb2Te3 are investigated. We found that the vacancy configurations that have rather small energy difference can exhibit contrast electronic property and different localized states near Fermi level. Furthermore, the migration of Sb atom and the lattice transformation accounting for the phase transition between cubic and rhombohedral Sb2Te3 have smaller energy barrier than those in Ge-Sb-Te compound, which should be responsible for the metastability of cubic Sb2Te3 and its rapid transition to the rhombohedral phase. Our results provide a comprehensive understanding of cubic Sb2Te3 and may offer new insight into the development of phase-change memory based on Sb2Te3.