Site-specific valence-band X-ray photoelectron spectra of a SrTiO3 single-crystal by X-ray standing wave technique

Site-specific valence-band X-ray photoelectron spectra of SrTiO3 (111) were successfully obtained by using X-ray standing wave technique. Contributions of the Ti and SrO3 derived states to the valence-band spectra were clearly separated. The spectra provided not only site-specific but also bulk-sensitive information on the SrTiO3 crystal because of the use of a high-energy synchrotron X-ray source (hν=4750 eV) for photoelectron excitation with the large escape depth. The electronic structures calculated by the DV-Xα method using a (Sr8Ti27O108)92− cluster model well reproduced the observed structures in the valence-band spectra. The partial density of states of both Ti and Sr ions in SrTiO3 were mainly distributed over the bottom of the valence-band to produce the covalent bonding with O ions.