Photoelectron energy-loss functions of SrTiO3, BaTiO3, and TiO2:: Theory and experiment -: art. no. 085101

We compare experimental O 1 s electron energy-loss structures below 30 eV of single crystalline SrTiO3, BaTiO3, and TiO2 with their theoretical electron energy-loss functions. The photoelectron energy-loss structures of in situ fractured surface in ultrahigh vacuum can be approximated by a sum of four components for SrTiO3 and BaTiO3, and of three components for TiO2. Electronic structures were calculated from first principles using the full-potential linearized augmented plane-wave method in the local-density approximation. The momentum matrix elements between Bloch functions were evaluated to determine the electron energy-loss functions. The theoretical electron energy-loss functions agree well with experimental spectra except a structure at around 20 eV of SrTiO3 and that at around 18 eV of BaTiO3. The difference of high binding energy peaks is explained from the positions of semicore states.