Growth Mechanism of BaTiO₃ Thin Film by Theoretical Calculation of Electronic Structure

The surface electronic structure of BaTiO₃ and the adsorption of oxygen ion have been calculated using the DV-Xα cluster method. We use the concept of embedded clusters to model the BaTiO₃ (001) surface, and O^2- adsorption and Ba²⁺ coadsorption on the surface. We calculate the valence electronic states for the surface and those involved in adsorption. Using Mulliken's population analysis it is found that the adsorption of oxygen ion on the surface weakens the covalent bonds between Ti and O in the BaTiO₃ substrate. In contrast, oxygen ion with coadsorbed Ba²⁺ ions results in stronger chemical bonding in the cluster than for the adsorption of only O^2- ion. The present results indicate that epitaxial BaTiO₃ thin films can be grown by simultaneous adsorption of groups of ions which have overall charge neutrality.