Substrate effect on the superconductivity of YBa/sub 2/Cu/sub 3/O/sub 7/ thin films

The interaction between the substrate and YBa/sub 2/Cu/sub 3/O/sub 7/ films made by ion beam sputtering and e-beam evaporation is found to significantly influence the superconducting transition temperature, T/sub c/. The substrates investigated are Al/sub 2/O/sub 3/, MgO, SrTiO/sub 3/, ZrO/sub 2/-9% Y/sub 2/O/sub 3/ (YSZ), and BaF/sub 2/. In the case of Al/sub 2/O/sub 3/, a spinel is formed at the interface and Al is found to be present in solution in the YBa/sub 2/Cu/sub 3/O/sub 7/. This reaction significantly depresses T/sub c/. For SrTiO/sub 3/, both Sr and Ti are found in the film without severely depressing the T/sub c/; this, however, depends on the annealing conditions. Although under similar conditions little interaction was observed for the MgO substrates, a moderate reduction in T/sub c/ was observed. An interaction zone of BaZrO/sub 3/ perovskite is formed at the interface between the YSZ substate and the 123 structure. In addition, Zr is found in solution in the 123 film. The presence of Zr has little effect on the T/sub c/. The films were characterized using Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), secondary ion mass spectroscopy (SIMS), x-ray and electron diffraction and resistance vsmore » temperature measurements.« less