Electron-Beam-Induced Formation of Oxygen Vacancies in Epitaxial LaCoO3 Thin Films

The formation of oxygen vacancies in heteroepitaxial LaCoO3 thin films deposited on different substrates was investigated by using electron beam irradiation in atomic-scale scanning transmission electron microscopy (STEM). As the electron beam irradiation intensified, distinctive dark stripe patterns were identified in high-angle annular dark-field STEM images, demonstrating the formation and subsequent ordering of oxygen vacancies. A comprehensive quantitative analysis of the lattice parameter changes verified the significant expansion of unit cells associated with the presence of oxygen vacancies. In particular, a uniform distribution of these expanded unit cells was observed in the films under large tensile strain. These experimental findings emphasize the significant role of strain in generating oxygen vacancies in perovskite oxide materials.