Fabrication and properties of large area Tl2Ba2CaCu2O8 superconducting thin film on sapphire substrate

Abstract

High quality large area Tl2Ba2CaCu2O8(Tl-2212)superconducting thin films were fabricated on CeO2 buffered two-side sapphire substrates. Using metallic cerium target as the sputtering source, CeO2 buffer film with c-axis orientation was deposited by radio frequency reactive magnetron sputtering, and the influence of preparation conditions on the structure and surface morphology of the CeO2 layer was studied. The Tl-2212 superconducting thin film was fabricated on CeO2 buffered sapphire substrate by direct current magnetron sputtering and post annealing. Scanning electron microscope showed that the film has a compact microstructure with uniform flat surface. The X-ray diffraction indicated that the film was pure Tl-2212 phase with c-axis perpendicular to the substrate surface, and epitaxially grown on the CeO2 buffered sapphire. The superconducting film exhibited excellent uniform electric properties. The critical transition temperature Tc was around 105 K, the critical current density Jc(77 K, 0 T) was around (1.2±0.1) MA/cm2 and (1.25±0.1) MA/cm2, respectively, and the microwave surface resistance Rs (77 K, 10 GHz ) of the film was as low as 390 μΩ.