Bi-Sr-Ca-Cu-O系超伝導膜の生成とCVD条件

概要

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Bi-Sr-Ca-Cu-O superconducting films were prepared on MgO (100) substrates by chemical vapor deposition using triphenyl bismuth and β-diketonates of Sr. Ca and Cu as source materials. The films composed of c-axis oriented 30 Å and 37 Å phases were prepared at 800°C. The films with indicating of the highest XRD intensity of the 37 Å phase exhibited a Bi:Sr:Ca:Cu molar ratio of around 2:2:3:4. Increase of oxygen partial pressure during film deposition at deposition rate of 0.2μm/h raised values of α which is the XRD intensity ratio of 37 Å phase as compared with 30 Å phase. However, values of α for the films prepared at a deposition rate of 0.1μm/h were around 0.7 and did not depend on the oxygen partial pressure from 2.5 to 60 Torr. At a deposition temperature of 800°C, the film having the highest value of the XRD intensity ratio of 37 Å phase was obtained. At deposition temperatures of 830-850°C, the 24 Å phase appeared with the 30 Å and 37 Å Phases. The onset temperature of superconducting transition was observed at around 110 K for the films containing the 37 Å phase. However, the films prepared at 800°C showed T<SUB>c</SUB> (resistivity zero: R=0) at 65 K. The highest T<SUB>c</SUB> (R=0) of 74 K was measured for the film prepared at 850°C.
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