Chemical vapor deposition of superconducting Bi-Sr-Ca-Cu-O films using fluorocarbon-based precursors
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Chemical vapor deposition of superconducting Bi-Sr-Ca-Cu-O films using fluorocarbon-based precursors Masanori Nemoto and Mitsugu Yamanaka Scientific Research Laboratory, Central Engineering Laboratories, Nissan Motor Co., Ltd., 1, Natsushima-cho, Yokosuka, Kanagawa 237, Japan (Received 30 May 1989; accepted 16 August 1989) Superconducting Bi-Sr-Ca-Cu-O thin films have been prepared for the first time by chemical vapor deposition using triphenyl bismuth and fluorocarbon-based chelates such as bis(hexafluoroacetylacetonate)strontium, bis(hexafluoroacetylacetonate)calcium, and bis(hexafluoroacetylacetonate)copper. After annealing in air, x-ray diffraction data reveal that the films deposited on (001) SrTiO3 substrates have preferential orientation of their crystalline c-axis perpendicular to the substrate surface. Four-probe resistivity measurements reveal the onset of superconductivity at 80 K and zero resistivity at 50 K.
The discovery of superconducting Bi-Sr-Ca-CuO with Tc values in the region of 105 K1 has stimulated great interest in the preparation of high quality, high Tc films, which are of interest for the fundamental study of high Tc superconductivity and also for the application to microelectronic devices. Up to now, high Tc superconducting films have been prepared mainly by physical vapor deposition such as sputtering,2 laser ablation,3 and electron beam evaporation4 or coevaporation.5 In addition, the growth of these films by chemical vapor deposition (CVD) has also been reported.6"8 Chemical vapor deposition offers the advantages of simple apparatus, amenability to large-scale processing, low deposition temperatures, and no requirements of high vacuum. Some metalorganic chelates are used as precursors in CVD. Good precursors need to have high vapor pressure. Hydrocarbon- or fluorocarbon-based chelates are sufficiently volatile to be used as precursors. The preparation of superconducting Bi-Sr-Ca-Cu-O thin films has been reported by CVD using hydrocarbon-based chelates but not using fluorocarbon-based ones. In the previous paper, we reported the successful growth of superconducting Y-Ba-Cu-O thin films by CVD using fluorocarbon-based chelates.9 In this communication, a point of issue is the choice of metalorganic chelate precursors. Triphenyl bismuth [Bi(Ph)3; Bi(C6H5)3] was employed as a bismuth source in the present study, and bis(hexafluoroacetylacetonate)copper [Cu(HFA)2; Cu(C5HF6O2)2] was selected as a copper source. As strontium and calcium sources, bis(hexafluoroacetylacetonate)strontium [Sr(HFA)2; Sr(C5HF6O2)2] and bis(hexafluoroacetylacetonate)calcium [Ca(HFA)2; Ca(C5HF6O2)2] were used. For comparison, Bi-Sr-Ca-Cu-O thin films were also J. Mater. Res., Vol. 5, No. 1, Jan 1990
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prepared using Bi(Ph)3, Cu(HFA)2, and hydrocarbonbased chelates such as bis(dipivaloylmethanate) strontium [Sr(DPM)2; Sr(CuH19O2)2] and bis(dipivaloylmethanate)calcium [Ca(DPM)2; Ca(CuHi9O2)2]. Here we report for the first time on the growth of superconducting Bi-Sr-
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