Effect of epitaxial strain on cation and anion vacancy formation in MnO

TL;DR

This study uses density functional theory to explore how biaxial strain influences cation and anion vacancy formation in MnO, revealing strain-dependent vacancy preferences and anisotropic defect ordering.

Contribution

It provides detailed insights into the interaction between biaxial strain and point defect formation in MnO, highlighting strain-induced vacancy preferences and defect ordering.

Findings

Compressive strain favors cation vacancy formation.

Small strains induce vacancy ordering along specific directions.

Strain influences anisotropic properties through defect arrangement.

Abstract

Biaxial strain in coherent epitaxial thin films can have a pronounced effect on the point defect profile in the film material. Detailed fundamental knowledge of the interaction of strain with point defects is crucial in understanding the stoichiometry and resulting properties of strained thin films. Here we investigate the effect of biaxial strain on the formation energy of cation and anion vacancies using MnO as a model system. Our density functional theory calculations show that, as expected from local volume arguments, compressive strain favours the formation of cation vacancies. Interestingly, we find that small compressive and tensile strains lead to ordering of the resulting holes along the in-plane and normal direction respectively, which should manifest in different anisotropic properties in the two strain states.