Impact of Point Defects on the Electronic Structure in Barium Titanate Thin Films

Abstract

This work presents the results of electronic structure calculation of barium titanate using the linearized augmented plane wave (LAPW) method implemented in the WEIN2K software. First principal calculations were made for the defect-free crystal and the crystal with two type of point defects: oxygen and titanium vacancies. According to the results of calculations, the presence of oxygen vacancies provides the n-type conductivity, while the titanium vacancies generate p-type conductivity. The formation energies of the titanium and oxygen vacancies were estimated to understand the possible effect of electric fields on the point defect creation. The results of ab-initio calculations were compared with experimental measurements of SrTiO3/La0.7Sr0.3MnO3/BaTiO3 heterostructures with epitaxial and polycrystalline barium titanate thin films performed by X-ray photoelectron spectroscopy (XPS). Analysis of acquired XPS spectra enables as to conclude the presence of oxygen vacancies in BaTiO3 thin films, manifests itself in changes in the cation peak shapes from Ti2p, Ti3p, Ba3d and Ba4d core levels, in accordance with the results of electronic structure calculations.