Textured superconducting thin films of bismuth cuprate by laser ablation method

The authors have prepared highly textured superconducting thin films from Bi1.5Pb0.5Ca3Sr2Cu4Ox (2324) on (100) YS-ZrO2 (Yttria stabilized zirconia) and Bi1.5Pb0.5Ca2Sr2Cu3Ox (2223) on LaAlO3 (100) and MgO (100) substrates at 650 degrees C by pulsed laser ablation method. These films showed 2212 type of phase of the (BiPb)2(Ca,Sr)n+1CunO2n+4+δ family with onset transition temperature (Tc) ∼ 110 K, confirming our earlier observations of 110 K superconductivity in a n = 2 bulk material. Thin films deposited from 2324 bulk target on YS-ZrO2 showed zero resistance temperature (Tc0) of 68 K but post annealing for one hour at 400 degrees C in oxygen improved Tco from 68 K to 82 K. Thin films from 2223 target on LaAlO3 (100) and MgO (100) exhibited a Tc0 of 65 K ad 74 K respectively while onset remained the same at 110 K. Further annealing at 400 degrees C for one hour in oxygen did not show any improvement in Tco. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford backscattering (RBS) channeling studies were performed on these films for correlation between crystal structure, microstructure and superconducting properties. X-ray diffraction patterns indicated 2212 type phase with a = 5.39 angstrom and c = 30.76 angstrom; preferential orientation of c-axis perpendicular to the substrate was observed. The lattice parameter and x-ray diffraction patterns were found to be invariant with annealing treatments