THE PROPERTIES OF CO-SPUTTERED YBA2CU3O7 AND CEO2 THIN-FILMS

We have investigated the morphology and superconducting properties of off-axis co-sputtered thin films of YBa2Cu3O7 and CeO2. The composite films were made with CeO2 concentrations up to approximately 43%. Morp hology investigations using x-ray diffraction and scanning electron mi croscopy suggest that films with less than 29% CeO2 may consist of a d istorted YBCO crystal structure with Ce being incorporated into the la ttice. Films with more than 29% consist of a new material phase. T-c a nd resistance ratio decreased with increasing CeO2 concentration. Degr adation of T-c after photoresist processing was observed for films wit h higher amounts of CeO2. However, this degradation was reversed and T -c improved beyond that of the as-deposited film by processing the fil ms with an oxygen plasma etch. The temperature dependence of the criti cal current near T-c showed two power law dependence regions with a cr ossover near 0.99 T-c for films having low concentrations of CeO2. Thi s crossover shifted to lower temperatures for films with higher amount s of CeO2. I-c's were decreased by small applied magnetic fields, and for some samples response was observed which was greater than 0.5 mA/G and increased with decreasing temperature. For a sample having 26% Ce O2, a 40% reduction in critical current for a 2 G applied field was ob served. These magnetic field responses indicate that this material may be a promising candidate for the development of Josephson vortex flow devices.