Domain boundaries in thin films of LiCoO₂ deposited on α-Al₂O₃ substrates

Abstract

The structure and properties of domain boundaries in epitaxial thin films of rhombohedral LiCoO₂ deposited on sapphire substrates are reported, based on a combination of atomic-level simulation and high-angle annular dark field scanning transmission electron microscopy. The results show that the domain boundaries are of an inverse antiphase type, and their high excess energies indicate they are not particularly stable. Examination of the film/substrate interface reveals that the domains form because steps on the nominally flat substrate displace one LiCoO₂ domain relative to its neighbors by one cation layer spacing.