Electronic structure of epitaxial (Sr,Ca)RuO3 films studied by photoemission and x-ray absorption spectroscopy -: art. no. 085108

Electronic structures of epitaxial (Sr,Ca)RuO3 thin films are studied by photoemission and x-ray absorption spectroscopy using synchrotron radiation. The Ru 4d spectral weights obtained by utilizing the Cooper minimum phenomena of photoionization cross-section reveal a strong mixing between Ru 4d and O 2p states as well as the signature of electron correlation effect near the Fermi level in both SrRuO3 and CaRuO3. However the electron correlation effect seems more important in CaRuO3 than SrRuO3. The detailed shapes of the valence band are found to depend on the sample cleaning methods, where the single-crystalline films cleaned by in situ annealing show more enhanced structures in the spectra than the scraped polycrystalline samples.