Preparation of High Tc Oxide Superconducting Tape by Rf Magnetron Sputtering
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PREPARATION OF HIGH Tc OXIDE SUPERCONDUCTING TAPE BY RF MAGNETRON SPUTTERING M.Fukutomi*,Y.Tanaka*,T.Asano*,H.Maeda*,and H.Takahara** *National Research Institute for Metals,Tsukuba Laboratories,Tsukuba-shi, Ibaraki,Japan **Mitsui Mining & Smelting Co.,LTD.,Central Research Laboratory,Ageo-shi Saitama,Japan ABSTRACT The feasibility of preparing YBaCuO films on metallic substrates is discussed in an attempt to fabricate a superconductfng tape. Deposition An amorphous MgO thin method employed was an rf magnetron sputtering. The highest zero resistance layer was found to be a promising buffer layer. temperaturg was 2 84.0 K in its as grown state, and a critical current density was 4.8xi0 A/cm at zero field and 77.4 K. Preliminary experiments using laser ablation technique were also carried out to obtain YBaCuO films at a rather high deposition rate. INTRODUCTION Besides electronic applications, thin film technologies of high-Tc superconductors have many other potential applications, including the fabrication of conductors for high field superconducting magnets, electromagnetic shields, etc. In this work, we report the growth of YBaCuO superconducting films on metallic substrates in an attempt to fabricate a superconducting tape[l,2]. Deposition method employed was a single- and threetarget rf magnetron sputtering. Particular attention was given to the preferential resputtering effect due to the bombardment of negative ions during sputtering. The substrate-cathode arrangement was described to High-rate deposition of YBaCuO achieve stoichiometric film composition. films was also attempted using laser ablation technique. DEPOSITION OF YBaCuO THIN FILMS AND RESULTS Preparation of buffer layer Effect of various buffer layer such as MgO and SrTi03 on the properties of high-Tc superconducting films has been described elsewhere[l,3], in brief, buffer layers were magnetron-sputtered onto the substrate using a sintered Of various buffer layers examined so compound target of each material. far, MgO thin layers have given the most promising results. In the present study, therefore, two kinds of buffer layer were examined; a (200) preferentially oriented and an amorphous MgO layer. Film preparation by single-target sputtering When high-Tc superconducting films are prepared by sputtering, we often observe a marked loss of film or compositional change directly above the target. Resputtering due to oxygen anion bombardment of the substrate One of the effective is thought to be responsible for these phenomena. approaches to circumventing this negative-ion problem is an rf magnetron sputtering in an off-axis geometry, in which the direct substrate bombardment Mat. Res. Soc. Symp. Proc. Vol. 169. s1990 Materials Research Society
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by energetic particles is avoided[4,5]. We have reported a successful growth of YBaCuO thin films on Hastelloy-X tape (11 cm in length) with a MgO buffer layer by placing the substrate in the region outside the negative ion impact area above the target[2]. In the present work, we attempted to make a long
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