Surface Study of High-Tc Superconducting Thin Films and Related Materials by In Situ Angle Resolved Photoemission Spectroscopy

Abstract

In-situ angle resolved X-ray photoemission spectroscopy has been performed on (100) oriented SrTiO3 single crystalline substrates and superconducting YBa2Cu3O7-δ epitaxial sputtered films with a,b-axis preferred orientation in order to determine composition of their outermost layers. For both of the specimens, the clean surfaces resulted from the in-situ measurements has caused the clear photoelectron diffraction phenomena. The single scattering cluster model has been examined to interpret the diffraction patterns. For the surface of SrTiO3 (100), the cleaning by the chemical etching with HCl and heat-treatment in vacuum should lead the TiO2 outermost layer. On the case of the YBCO films, the photoelectron escape angle dependence of the relative intensities of the Y 3d, Ba 3d and Cu 2p core emissions has shown a better agreement with the calculation on the surface with the Cu-O outermost layer than the (Y, Ba)-O in the outermost one.