Interplay between strain, defect charge state and functionality in complex oxides

TL;DR

This study uses first-principles calculations to explore how strain and defect charge states interact in complex oxides, revealing how charge manipulation can control defect behavior and material functionalities.

Contribution

It demonstrates that defect charge states can be tuned to influence strain and defect distribution, enabling reversible control of functionalities in epitaxial films.

Findings

Charge state affects defect-strain interactions

Strain influences defect charge stability

Field-effect gating can reversibly control defect charge states

Abstract

We use first-principles calculations to investigate the interplay between strain and the charge state of point defect impurities in complex oxides. Our work is motivated by recent interest in using defects as active elements to provide novel functionality in coherent epitaxial films. Using oxygen vacancies as model point defects, and CaMnO$_3$ and MnO as model materials, we calculate the changes in internal strain caused by changing the charge state of the vacancies, and conversely the effect of strain on charge-state stability. Our results show that the charge state is a degree of freedom that can be used to control the interaction of defects with strain and hence the concentration and location of defects in epitaxial films. We propose the use of field-effect gating to reversibly change the charge state of defects and hence the internal strain and corresponding strain-induced functionalities.