Observation of nonuniform current transport in epitaxial YBa2Cu3O7-x film near the superconducting transition temperature

摘要

We have studied the local transport properties in an epitaxial YBa2Cu3O7-x, (YBCO) film on LaAlO3 (LAO) using variable temperature scanning laser microscope (VTSLM) near the superconducting transition. A map of the superconducting transition temperature (T-c*) is generated from a series of VTSLM images. The map of T-c* indicates there are inhomogeneities in the film large enough to create nonuniform current flow near the superconducting transition. The evaluated T-c* 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 T-c* 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. (C) 2004 Elsevier B.V. All rights reserved.