Comparing the Impacts of Strain Types on Oxygen-Vacancy Formation in a Perovskite Oxide via Nanometer-Scale Strain Fields

The utilization of an in-plane lattice misfit in an oxide epitaxially grown on another oxide with a different lattice parameter is a well-known approach to induce strains in oxide materials. However, achieving a sufficiently large misfit strain in this heteroepitaxial configuration is usually challenging, unless the thickness of the grown oxide is kept well below a critical value to prevent the formation of misfit dislocations at the interface for relaxation. Instead of adhering to this conventional approach, here, we employ nanometer-scale large strain fields built around misfit dislocations to examine the effects of two distinct types of strains─tension and compression─on the generation of oxygen vacancies in heteroepitaxial LaCoO3 films. Our atomic-level observations, coupled with local electron-beam irradiation, clarify that the in-plane compression notably suppresses the creation of oxygen vacancies, whereas the formation of vacancies is facilitated under tensile strain. Demonstrating that the defect generation can considerably vary with the type of strain, our study highlights that the experimental approach adopted in this work is applicable to other oxide systems when investigating the strain effects on vacancy formation.