Surface Morphology and Crystal Structures of As-Grown BiSrCaCuO Thin Films Prepared by RF Magnetron Sputtering from Three Targets

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Abstract
As-grown superconducting BiSrCaCuO thin films were grown at 650°C on MgO(100) substrates by RF magnetron sputtering from three targets. The substrate was rotated over the three targets: Bi3Sr2Ca2Cu3O x , Bi2Sr3Ca3Cu3O x and Bi2Sr2Ca2Cu4.5O x . By adjusting the staying time of the substrate over each target, it was possible to precisely control the chemical composition of the thin film. This paper describes the superconducting properties, surface morphology and crystal structures of sputtered films formed by varying the staying time. X-ray diffraction measurement showed that the crystal structure could be changed by varying the staying time. The film with the optimum composition showed zero resistivity at 75 K and had an exceedingly smooth surface. This film had the mixed phase which is considered to be a stacked structure consisting of a high-T c phase and a low-T c phase.