Highly oriented Bi-based thin films with zero resistance at 106 K

The authors report on the fabrication and characterization of nearly single-phase superconducting Bi₂Sr₂Ca₂ Cu₃O_x thin films. The films are DC-magnetron-sputtered from heavily Pb-doped (Pb/Bi molar ratios up to 1.25), sintered targets on unheated MgO, SrTiO₃, CaNdAlO₄, and SrLaAlO₄/sur single crystals. For the films grown on the (100)-oriented MgO substrate, less than 1 h of annealing in air at 870°C was sufficient to obtain more than 90% of the 110-K-phase material, with highly c-axis-oriented crystalline structure and zero resistivity at 106 K. The films fabricated on the other substrates also exhibited a narrow superconducting transition and were fully superconducting above 100 K, but they consisted of a mixed-phase material with a large percentage of the 80 K phase