オフアクシスマグネトロンスパッタリング法によるYBCO薄膜の作製 (酸化物超伝導物質と材料<特集>)

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YBa2Cu3Ox (YBCO) thin films have been grown on (100) MgO substrate by off-axis magnetoron sputtering. Critical temperature(Tc) of YBCO films strongly depended on substrate temperature, sputtering gas composition and total pressure and “in-situ” annealing conditions. When substrate temperature was 700°C, and gas composition and total pressure were Ar+50%O2 and 200mTorr respectively, YBCO films of Tc=77.5K was obtained. XRD pattern of this film showed sharp (00l) peaks showing very high c-plane orientation. Scanning tunneling microscopic (STM) image of the films showed growth spirals which were aligned to one direction. The size of the growth spirals were 150-300nm. On the other hand, when substrate temperature was 650°C, Tc was 25K and its XRD pattern showed both (h00) peaks and (00l) peaks. STM image of this film showed both textured structures and growth spirals. We presumed that c-plane crystal shows growth spiral and a-plane one shows textured structure in sputter grown YBCO films. Patterning of YBCO thin films by photolithography did not cause the reduction of Tc.
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