In-Situ Growth and Structure of High-TcSuperconducting Thin Films

Abstract

Growing manner of YBa 2 Cu 3 O 7−x (YBCO) thin films on SrTiO 3 (100) and MgO(100) by reactive evaporation method was investigated by means of in situ reflection high energy electron diffraction (RHEED) and X-ray diffraction. In-situ RHEED observation showed that the formation of perovskite structure occurred even for initially deposited two atomic planes and the YBCO crystal grew in the layer-by-layer manner. It was demonstrated by RHEED patterns that the in-plane lattice of YBCO on seriously lattice mismatched MgO was initially strained for the matching with MgO and changed abruptly to the lattice parameter of the tetragonal YBCO bulk with increasing thickness. X-ray analysis of the 100 A thick superconducting film on SrTiO 3 (100) revealed no orthorhombic distortion and the in-plane lattice parameter was close to that of SrTiO 3 . On the other hand, the 100 A superconducting film on MgO was found to have orthorhombic symmetry