Oxygen vacancy dipoles in strained epitaxial BaTiO3 films

The existence of out-of-plane-oriented oxygen vacancy dipoles was experimentally established in (001) perovskite epitaxial films of ferroelectric barium titanate by analyses of the crystal and electronic structure as well as the ferroelectric and optical properties. The formation of the defects was shown to occur in the presence of in-plane compressive strain and oxygen-deficient deposition conditions. The in-plane compressive strain was suggested to favor the formation of oxygen vacancies V_O in the Ba-O planes and thus stabilize the out-of-plane orientation of the dipolar (V⁺²_O−Ti³⁺)⁺ defects.