As-Grown Superconductivity of BiSrCaCuO Thin Films Prepared by Magnetron Sputtering with Three Targets: Bi2+a(SrCa)2Cu3Ox, Bi2(SrCa)2+bCu3Ox and Bi2(SrCa)2Cu3+cOx (a=b=1, c=1.5)

Superconducting BiSrCaCuO thin films were grown on MgO(100) substrates by magnetron sputtering with three targets. In order to precisely control the chemical composition of the metal elements, these three targets were simultaneously discharged; the heated (650°C) substrate was rotated above these targets. The superconducting transition temperature (zero resistivity) was 75 K in the as-grown state for the optimized sample. From the X-ray diffraction, The c-axis of the film was highly oriented normal to the substrate. The surface of the film was much smoother than that of the film grown with a single target.