Theoretical investigation on thermodynamic properties of ZnO1−xTex alloys

Abstract

In this study, the formation energy, phase diagram (with/without phonon contribution) and the relationship between bond stiffness and bond length for wurtzite (WZ) and zincblende (ZB) structures of ZnO1−xTex (0 ⩽ x ⩽ 1) alloys have been investigated by combining first-principles calculations and cluster expansion method. The formation energy of ZnO1−xTex alloys is very high in both structures, which means that it is difficult for ZnO and ZnTe to form stable ternary alloys ZnO1−xTex. In the phase diagrams, both structures do not have stable phase of ternary alloys and ZnO1−xTex ternary alloys can only exist in the form of metastable phase. These results indicate that ZnO and ZnTe easily form solid solubility gap when they form alloys. After considering vibrational free energy, we found the solubility of Te in ZnO and O in ZnTe was increased and the vibrational entropy improved the solubility furthermore. The phonon contribution is not ignorable to improve solid solubility. The phonon density of states was analyzed for ZnO1−xTex alloys and the contribution from vibrational entropy was discussed.