X-RAY PHOTOELECTRON STUDY OF THE NONEQUIVALENT OXYGEN LATTICE SITES IN Y-BA-CU OXIDE THIN-FILMS

X-ray photoelectron spectroscopy was used to investigate the non-equivalent oxygen sites in thin films of the perovskite-type material YBa2Cu3O7-delta grown epitaxially on single crystal wafters of SrTiO3. The method previously developed to distinguish among the structurally non-equivalent oxygen sites for bulk YBa2Cu3O7-delta materials was applied to the thin films. The films contained either strontium or strontium and titanium, depending on the fabrication procedure. One of the films appears to be composed of mixed orthorhombic and tetragonal crystals, while the other film appears to be composed of orthorhombic and possibly oxygen deficient orthorhombic crystals. These determinations were corroborated by x-ray and magnetic measurements. The binding energy differences between the O 1s electrons involved were determined to be the same as in the bulk orthorhombic and tetragonal materials, but the absolute values were uniformly lower.