Fabrication and Properties of Double-Side Tl2Ba₂CaCu₂O₈ Thin Film on CeO₂ Buffered Sapphire Substrate

The double-side Tl₂Ba₂CaCu₂O₈ (Tl-2212) superconducting thin films were fabricated on CeO₂ buffered sapphire substrates. The reactive magnetron sputtering technique was used to grow CeO₂ buffer thin films on sapphire substrates. Making use of the metal cerium as a sputtering source, the depositing rate is much higher compared with the CeO₂ target. The Tl-2212 thin films on CeO₂ buffered sapphire substrates were fabricated by a dc magnetron sputtering and post-annealing process. The x-ray diffraction indicates that the thin film is pure Tl-2212 phase with the c-axis perpendicular to the substrate surfaces, and epitaxially grown on the CeO₂ buffered sapphire. The critical transition temperature T_c is around 106 K, the critical current density J_c is around 3.5 MA/cm² at 77 K, and the microwave surface resistance R_s at 77 K and 10 GHz of the film is as low as 390 μΩ