Mechanisms for oxygen vacancy defect migration in SrTiO3/NiO heterostructures: Effect of interface layer chemistry and misfit dislocation structure

Abstract

Perovskite-based oxide heterostructures display promising properties resulting from interface phenomena, making them good candidates for next-generation solid oxide fuel cell electrolytes. Among the different features exhibited by these interfaces, misfit dislocations play an important role in influencing ionic transport, yet their role remains poorly understood, a phenomenon also observed in rock salt–perovskite interfaces. In SrTiO3/NiO heterostructures, we investigate oxygen vacancy migration near misfit dislocations using atomistic simulations in conjunction with a high-throughput nudged elastic band-based framework. By comprehensively mapping activation energy barriers across different interfacial chemistries and asymmetric structural features, we explore how the dislocation structure, which is dependent on the local interfacial chemistry, modulates oxygen vacancy migration. This study aims to shed light on the role of dopants, oxygen vacancies, interfacial chemistry, and extended defects in shaping ionic migration at the atomic scale. Misfit dislocations are often considered thermodynamic sinks for oxygen vacancies, oftentimes hindering ionic conductivity at such interfaces. We report dynamic behavior at interfaces that is largely dependent on the local coordination environment, challenging this conventional perspective. The study attempts to bridge the crucial gap in understanding interface-governed ion transport mechanisms in complex oxide heterostructures.