X-ray photoelectron spectra, theoretical band structures, and densities of states for BaTiO3and KNbO3

Abstract

X-ray photoelectron spectra of the valence bands and core levels for electron binding energies ranging from 0 to 45 eV, are presented for the two perovskite-type compounds BaTi${\mathrm{O}}_{3}$ and KNb${\mathrm{O}}_{3}$. Theoretical band structures and densities of states are calculated using a parametrized tight-binding method. The validity of the comparison between theoretical results and experimental valence-band spectra is discussed. The effects of the various interatomic interaction matrix elements are analyzed and theoretical results are also presented for SrTi${\mathrm{O}}_{3}$ in order to compare this work to earlier calculations. Photoionization cross sections are introduced in the densities-of-states computations: their contribution in modulating the valence-band shape is much more significant for KNb${\mathrm{O}}_{3}$ than for BaTi${\mathrm{O}}_{3}$. The present densities of states seem to reproduce in an adequate way the main structures of the experimental valence-band spectra.