X-ray photoemission study of the infinite-layer cuprate superconductor Sr0.9La0.1CuO2

The electron-doped infinite-layer superconductor Sr0.9La0.1CuO2 is studied with x-ray photoemission spectroscopy (XPS). A non-aqueous chemical etchant is shown to effectively remove contaminants and to yield surfaces from whi ch signals intrinsic to the superconductor dominate. These data are compare d to measurements from hole-doped La1.85Sr0.15CuO4, from undoped La2CuO4, a nd from electron-doped Nd1.85Ce0.15CuO4-delta. The Cu 2p core level is more consistent with a lower value of the O 2p --> Cu 3d charge transfer energy Delta than in hole-doped cuprates. A clear Fermi edge is observed in the v alence band region.