Formation of Sputtered Y-Ba-Cu-O Superconducting Thin Film on Metal Substrate
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FORMATION OF SPUTTERED Y-BA-CU-O SUPERCONDUCTING THIN FILM ON METAL SUBSTRATE. H. HAYAKAWA, Y. IIJIMA, N. SADAKATA AND 0. KOHNO Materials Research Laboratory, Fujikura Ltd. 1-5-1, Kiba, Koto-ku, Tokyo 135, Japan
ABSTRACT YIBa 2 CU 3 O7 _x superconducting composites have been prepared on metallic substrate by rf magnetron sputtering method. Buffer layer of thin SrTi03 layer between superconducting film and the substrate was found to be effective to realize superconductivity. Preferable grain alignment of 3 c-axis2 The critical current density at 77K was 2.2x10 A/cm was also obtained. with Tc at 83K, and it was found that the thicker films had the higher Jc values. INTRODUCTION For the application of the high temperature superconducting materials, it is important to form the substance into practical shape[i]. To fabricate composites on long flexible substrate without diminishing excellent superconducting performance is necessary for development of conductor. Metal alloy tape is useful because of its flexibility and thermal properties as a substrate for conductor. Meanwhile, films of aligned grains with preferred orientation with high critical current density have been reported through thin film processing [2-6]. Sputtering is one of the method to fabricate thin films with excellent properties, however, the thin layer of the films on the substrate may be easily contaminated by the diffused elements from the substrate during the deposition when the substrate is metallic[7]. In order to eliminate the degradation of the films, placing intermediate buffer layer which may reduce the interaction was found to be effective to realize good superconductivity. In this paper, we report the effect of the intermediate buffer layer of SrTiO3 on nickel based alloy for YiBa 2 Cu307-x superconducting composites. EXPERIMENTAL Hastelloy-C276 was used for this experiment as substrates. The size of the substrates were typically 10mm in width, 18mm in length and 1mm in thickness. The depositing surface was polished smoothly by diamond paste before the film preparation. The polished surface were then supersonically cleaned in distilled water, methyl-alcohol and acetone. Two thin film layers, one was SrTiO3 as a buffer and the other was Y1Ba2Cu307_x as a superconductor, were prepared by rf sputtering method. SrTiO 3 layer was deposited on the clean surface of the substrate using one SrTiO 3 target under the condition listed in table 1. YIBa2Cu307-x layer was deposited on the SrTiO3 buffer layer by the same sputtering apparatus using multi-targets of Y2 0 3 , BaCuO 2 and Cu. The targets were set facing the revolving substrates holder. Table 2 shows the sputtering condition of Y1Ba2Cu 3 07_x layer deposition. The time for the sputtering was from 4 to 20 hours yielding the layer from 0.7 to 3.2 micrometer in thickness. For the obtained multi-layered composites, crystal orientation of the films were analyzed by x-ray diffractometry. Observation of the surface by microscope was also performed. Critical temperature and critical current Mat. Res. S
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