SPATIAL VARIATION OF THE CRITICAL CURRENT-DENSITY OF THE HIGH-TC SUPERCONDUCTING THIN-FILMS

Low-temperature scanning electron microscopy (LTSEM) is a promising measuring technique for probing the spatial distribution of the superconducting properties of high T(c) thin films. In the presented article we have given some experimental observations on the spatial variation of the critical current density of two kinds of high T(c) thin films using a LTSEM. The results show that in the polycrystalline TlBaCaCuO film prepared by dc magnetron sputtering, the maximum local critical current density is about 3-4 times greater than the minimum local critical current density. The microstructure analysis implies that the strong inhomogeneous critical current density distribution in the TlBaCaCuO film is due to its granular structures and the existence of several structural phases. For c-axis oriented epitaxial YBaCuO thin film deposited in situ by laser ablation, the results indicate a less inhomogeneous critical current density distribution. The maximum local critical current density is less than 1.5 times the minimum local critical current density in the epitaxial thin film.