Effect of dopants on the structure and properties of Ge 2Sb 2Te 5 studied by Ab initio calculations

Abstract

Ge 2Sb 2Te 5 is technologically important for phase-change random access memory applications. In this work, the effect of doping Ag, Cd, In and Sn on the structure and chemical bonding of Ge 2Sb 2Te 5 has been studied by ab initio calculations. It has been shown that the 3.7 at.% dopants drastically weaken the Te–Te bond strength in the–Te–(vacancy)–Te–configuration while maintaining its rocksalt symmetry. According to the analysis of formation energy, doping at the Ge site of Ge 2Sb 2Te 5 phase is more favourable. The doped Ge 2Sb 2Te 5 phases demonstrate either semiconductor or metallic behavior, which is attributed to the valence electrons of the dopants that mainly contribute to either the conductivity or chemical bonding.