Formation of As-Grown YBaCuO Thin Films by RF Magnetron Sputtering from Three Targets

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Abstract
As-grown YBaCuO thin films with 500 Å thickness have been formed at 620°C on MgO(100) substrates by RF magnetron sputtering from three targets: Y1.5Ba2Cu3O x , Y1Ba3Cu3O x and Y1Ba2Cu4.5O x . The chemical composition can be precisely controlled by this method. A smooth surface was obtained by adjusting the chemical composition. Zero resistivity was observed at 81 K for the best superconducting film. The films with a slightly Cu excessive composition showed somewhat higher T c(zero) than the stoichiometric film. X-ray diffraction spectra of sputtered films did not change distinguishably upon varying of the chemical composition when the value of Ba/Y ranged from 1.5 to 2.3 and the value of Cu/Y ranged from 1.8 to 3.3. The c-axis of the film was highly oriented normal to the substrate surface, and the c-axis lattice constant was equal to that of a bulk sample.