Observation of Nonuniform Current Transport in Epitaxial YBa2Cu3O(7-x) Film Near the Superconducting Transition Temperature

摘要

We have studied the local transport properties in an epitaxial YBa2Cu3O(7-x) (YBCO) film on LaAlO3 (LAO) using variable temperature scanning laser microscope (VTSLM) near the superconducting transition. A map of the superconducting transition temperature (Tc) is generated from a series of VTSLM images. The map of Tc indicates there are inhomogeneities in the film large enough to create nonuniform current flow near the superconducting transition. The evaluated Tc varies between 90.3 and 91.0 K in the film. Even though such change in T(*)c is not large enough to be detected by other localized compositional and structural characterization techniques, this along with an area of lower Tc and/or higher resistance affects current flow near the superconducting transition temperature as shown in VTSLM images. This inhomogeneity may be caused by slight variations of the stoichiometry and/or oxidation of the YBCO film.