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