Bi-Sr-Ca-Cu-O Compositional Modulation and Multilayered Film Synthesis by Plasma Controlled Sputtering
Compositionally modulated Bi-Sr-Ca-Cu-O films were prepared by a method in which the target area to be sputtered can be controlled by varying the distribution of magnetic field over the target. When a binary target comprised of an inner Ca1.0Cu1.5Ox and an outer Bi1.6Sr1.0Oy disks was used, the deposited film composition could be varied successively from Bi-Sr rich to Ca-Cu rich by controlling the magnetic coil currents. Based on this result, films accumulating predominant (Bi-Sr-O) and (Ca-Cu-O) bilayers were deposited continuously on MgO(l00) substrates by periodical change of the coil currents. The film designed to have 100 repetitions of 10Å thick Bi-Sr rich and l0Å thick Ca-Cu rich layers has an actual periodicity of about 19Å by the analysis with low angle X-ray scattering. The films deposited at 200°C were almost insulating in the as-grown state, but they turned to be superconducting by the annealing at temperatures of 880–900°C in air. The annealed films have strong c-axis orientation normal to the substrate, resistivities of a few m Ω cm at room temperature, and zero resistivity temperatures higher than 70K.
KeywordsMultilayered Film Actual Periodicity Annealed Film Coil Current Homogeneous Film
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- 5.H.Koinuma, H.Nagata, A.Takano, M.Kawasaki, and M.Yoshimoto, “Preparation of Compositionally Modulated Bi-Sr-Ca-Cu-O Multilayered Films by Plasma Controlled Sputtering,” to be published in Jpn. J. Appl. Phys., 27 (1988).Google Scholar
- 8.H.Negata, A.Takano, M.Kawasaki, M.Yoshimoto, and H.Koinuma, “Preparation of Bi-Sr-Ca-Cu-O Thin Films by Sputtering under Variable Magnetic Field,” submitted to Communications of J. Amer. Cer. Soc.Google Scholar