MODIFICATION OF THE X-RAY PHOTOEMISSION SPECTRUM OF IN-SITU DEPOSITED THIN-FILMS OF Y1BA2CU3O7-Y FOR VARIOUS OXYGEN TREATMENTS

We have grown thin films of the Y1Ba2Cu3O7-y superconductor onto MgO and LaGaO3 substrates by off-axis sputtering. The films were all deposited under the same conditions, but were cooled in various oxygen pressures resulting in films with superconducting transition temperatures from 85 K to nonsuperconducting. The samples have been examined by x-ray photoemission spectroscopy without exposing the samples to air. We have characterized the core levels of Y, Ba, Cu, and O and the Auger parameter of Ba, Cu, and O as a function of the oxygen pressure used during cooldown. We find that the core lines sharpen and the Auger parameter for copper reduces as the oxygen pressure is decreased. We interpret this latter result as a possible change in the valence state of copper. We also see a variation in the valence structure.