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%. Morphology investigations using x-ray diffraction and scanning electron microscopy suggest that films with less than 29% CeO2 may consist of a distorted YBCO crystal structure with Ce being incorporated into the lattice. Films with more than 29% consist of a new material phase. T-c and resistance ratio decreased with increasing CeO2 concentration. Degradation of T-c after photoresist processing was observed for films with higher amounts of CeO2. However, this degradation was reversed and T-c improved beyond that of the as-deposited film by processing the films with an oxygen plasma etch. The temperature dependence of the critical current near T-c showed two power law dependence regions with a crossover near 0.99 T-c for films having low concentrations of CeO2. This crossover shifted to lower temperatures for films with higher amounts 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% CeO2, a 40% reduction in critical current for a 2 G applied field was observed. These magnetic field responses indicate that this material may be a promising candidate for the development of Josephson vortex flow devices.