Preparation of Superconducting Tl1Ba2Ca3Cu4Ox Thin Films by RF Magnetron Sputtering

Superconducting thin films of the Tl-Ba-Ca-Cu-O system with a single 1234 phase were prepared on a (100) MgO substrate by rf magnetron sputtering from a sintered Tl2Ba1Ca2Cu3O x target and subsequent annealing. X-ray diffraction analyses indicated that the films thicker than 5 µm which underwent annealing at 900–910°C contained the 1234 phase with a high degree of the c-axis orientation normal to their surface. The c-axis lattice constant was determined to be 19.05 Å. The best superconducting properties were obtained for the 5- µm thick films annealed 900°C for 1 min with an onset critical temperature at about 120 K and a zero-resistivity temperature at 113 K.