Superconducting properties of Tl-Ba-Ca-Cu-O films on silver substrates

Films of Ba-Ca-Cu-O have been RF-magnetron-sputtered onto Consil 995 substrates. A postdeposition anneal in an overpressure of Tl produces the superconducting 1212 and 2212 phases. Varying the annealing procedures changes the electrical properties of the final films dramatically. Dynamic impedance, a novel approach to the electrical characterization of these films on a conductive substrate, is discussed and compared with SEM (scanning electron microscope), XRD (X-ray diffraction) and RBS (Rutherford backscattering) measurements as a function of differing annealing protocols. The improvement in the superconducting responses as a function of annealing procedures correlates well with the improved morphology observed in the SEM photographs. Also, the XRD data show increased c-axis material with the C annealing protocol.