Synthesis and superconducting properties of Tl-Ba-Ca-Cu-O films

Tl-Ba-Ca-Cu-O superconducting films were synthesized by sputtering either from a single target or from two oxide targets in a symmetric configuration. Films were zero resistance T/sub c/ of up to 122 K were obtained after various postannealing treatments at 870-950 degrees C under an oxygen atmosphere. The composition of the films is not very homogeneous on the submicrometer scale. The critical current of these films at 77 K is in the 10/sup 3/-A/cm/sup 2/-10/sup 4/-A/cm/sup 2/ range, which is much smaller than that of films prepared on SrTiO/sub 3/ and LaAlO/sub 3/ substrates. The low critical current density in these films is probably due to the granularity in the films. The morphology, structure, and magnetic and superconducting properties of the films were studied. Films prepared by two different sputtering techniques have similar results which depend mostly on the film compositions and their annealing conditions. It is found that the induced magnetic flux in the film decreases rapidly with increasing temperature, indicating weak flux pinning.