Defect Analysis In Substrate Materials for High Tc Superconducting Thin Films

Abstract

AbstractMany defects in high Tc superconducting films propagate from the substrate through to the film surface, disturbing the epitaxy at the interface and adversely affecting the physical properties of the film, particularly Jc. In this study the surface of Magnesium Oxide (100) single crystal substrates with different preparative treatments have been investigated using optical cathodoluminescence microscopy (CL), with a view to establishing its effect on the deposition of thin films of YBa2Cu3O7-δ superconductors.CL excitations due to mechanically and chemically induced defects in the MgO substrate crystals are observed by optical CL microscopy. Several pre-deposition treatments have been compared in this way to determine the best preparation route for the substrates. Jc measurements indicate that the substrate surface quality is an important parameter in the production of high quality thin films especially for the fabrication of devices.It is concluded that CL provides a powerful and rapid tool for MgO quality assessment before thin film deposition.