Bi-Sr-Ca-Cu-O superconducting films were prepared by rf magnetron sputtering using a target with modulated composition and successive annealing in oxygen. The resistivity and Cu valence of the films varied before and after annealing. The zero-resistance temperature of the films was 10 K before the annealing, and rose up to 96 K (midpoint 105 K) after annealing. Essentially no change in the characteristic layer spacing (d value) of = 18 A, corresponding to c/2, was observed before and after annealing as seen by x-ray diffraction. The eu valence of the films was investigated by x-ray photoemission before and after annealing. The photoemission core-level spectra and LMM Auger emission spectra revealed that the Cu valence after annealing became larger than that obtained before annealing. The superconductivity obviously is correlated with the Cu valence of the films.
Thin films of Y-Ba-Cu-O system have been prepared by rf-magnetron sputtering technique. The films were crystallized through post annealing and superconductivity was appeared. The film on R-plane of sapphire showed superconducting transition with an onset temperature at 94 K and zero-ρ state was achieved below 70 K.
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