Search

Abstract: The electronic structure of epitaxial SrRuO3 thin films annealed at 300°C in ultra high vacuum is studied by resonant photoemission spectroscopy using synchrotron radiation. The valence band photoemission spectra show a good agreement with theoretical band structure calculations indicating a good quality of the film surface. A method was proposed, which allows extracting the partial density of states in the case of weak and broad resonance. The Ru 4d spectral weights obtained experimentally are in a very good agreement with theoretical predictions, confirming a strong mixing between Ru 4d and O 2p states, as well as the signature of electron correlation near the Fermi level in SrRuO3. [Copyright &y& Elsevier]

Abstract: The resonant photoemission spectroscopy was used to study the surface electronic structure under La 4d→4f and Ni 3p→3d photo-excitation of thin LaNiO3−δ films after annealing in ultrahigh vacuum above dehydration temperature. The giant resonance in La 5p and La 5s peaks intensity observed at excitation energy corresponding to a La 4d→4f threshold is accompanied by resonance of the N4,5O2,3O2,3 and N4,5O2,3V Auger peaks. The enhancement in the intensity of valence band maxima (at about 6eV) may be explained by the small mixing of the La 5d ionic character to the O 2p valence band. The week resonant features observed in the valence band spectra under Ni 3p→3d threshold indicate the loss of nickel species at the LaNiO3−δ film surface after heat treatment. [Copyright &y& Elsevier]

Abstract: Thin LaNiO3− δ films with pseudocubic (100) preferred orientation were prepared by reactive DC magnetron sputtering and in situ annealed in O2 and vacuum. X-ray photoelectron spectroscopy (XPS) was used to determine the variation in composition of the films under high-temperature annealing. The experimental O 1s spectrum of LaNiO3− δ films was analyzed in terms of “O2−”, “O−”/“(OH)−”, and weakly adsorbed oxygen species. It was shown that the change in the type of conductivity from the metallic to the semiconducting one is accompanied by a marked increase in the intensity of the lateral (∼531eV) peak of oxygen. These variations in conductivity and surface composition were attributed to the loss of lattice oxygen with subsequent adsorption from ambient air “O−” and “(OH)−” anions and weakly adsorbed oxygen species. [Copyright &y& Elsevier]