Superconductivity in thin films of Bi-Sr-Ca-Cu oxide deposited via laser ablation of oxide pellets

We have grown superconducting films on the technologically important sapphire substrates by CO₂ pulsed laser ablation from fully superconducting targets of Bi₂Sr_3-xCa_xCu₂O_y followed by appropriate post-annealing. The composition of the films was found to deviate slightly from the target. Nevertheless, films with metallic resistivity decreasing between room temperature and 95 K, T_c(onset) of about 90 K and T_c(zero) of 72 K have been obtained. Magnetoresistance measurements in fields up to 12.85 T give a value of dH_c2/dT of 1.6 T/K, which is intermediate between reported values of parallel and perpendicular H_c2 of fully aligned thin films. The implied partial orientation is consistent with the morphology seen by scanning electron microscopy.