Influence of substrate annealing on the epitaxial growth of BaTiO3 thin films by metal-organic chemical vapor deposition

BaTiO3 thin films were deposited by metal-organic chemical vapor deposition at 840 degrees C on two differently treated (100) MgO single crystal substrates, One MgO substrate was only mechanically polished and the other substrate was polished and then annealed at 1100 degrees C for 4 h in oxygen, Observation by transmission electron microscopy showed that the BaTiO3 thin film deposited on the unannealed substrate was fine-grained and that the whole film was epitaxial (100) in nature, In contrast, the film deposited on the annealed substrate consisted of large, (100)-oriented, epitaxial grains within which were distributed (110)-oriented grains with random in-plane orientations. These differences in BaTiO3 films deposited on differently treated substrates are discussed with reference to the surface structure of the MgO substrate and nucleation kinetics of BaTiO3 thin films on MgO.