Surface Analysis of YBa2 Cu30 Thin Films with Rheed-Traxs

Abstract

AbstractTotal Reflection Angle X-Ray Spectroscopy with Reflection High Energy Electron Diffraction (RHEED-TRAXS) is a highly sensitive method for surface analysis. Yba2Cu3O7-x films of less than 1 unit cell average coverage can be detected by its characteristic x-rays. We grew YBCO films on MgO substrates by laser-ablation with two different kinds of surface morphology; one had few particles on a flat surface and the other had many long and narrow islands on the surface which we call linear islands. We measured the take-off angle dependence of TRAXS on these films. For the YBCO films with linear islands the intensities of YLα, BaLα and CuKα x-ray lines have shoulders at the critical angles given by a theoretical formula. For the YBCO films with smooth surfaces, only the BαLa intensity had a sharp peak at the critical angle. The result suggests that a BaO layer terminates YBCO films, or that a chemical reaction occurs at the surface and Ba compounds is produced.