In-situ growth of yba 2 cu 3 o 7-x films by metal organic chemical vapor deposition using vertical, high-speed rotating
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IN-SITU GROWTH OF YBa2CU307-x FILMS BY METAL ORGANIC CHEMICAL VAPOR DEPOSITION HIGH-SPEED ROTATING DISK REACTOR. USING VERTICAL, D. W. Noh*, B. Gallois*, Y. Q. Li*, C. Chern**, B. Kear**, G. S. Tompa***, P. Norris***, and P. Zawadzki***, * Stevens Institute of Technology, Dept. of Materials Science and Engineering, Hoboken, NJ ** Rutgers University, Dept. of Materials Science, Piscataway, NJ *** EMCORE Corp., 35 Elizabeth Ave., Somerset, NJ
ABSTRACT Superconducting thin films of YBa2Cu307-x were grown on MgO (100) and YSZ(100) substrates without post-annealing by metal organic chemical vapor deposition using vertical, high-speed (1100 rpm) rotating disk reactor. The source materials were Ba(tmhd)2, and Cu(tmhd)2, which were kept at 135 oC, Y(tmhd)3, 240 oC, and 120 °C respectively. The precursors were transported using nitrogen as the carrier gas and introduced separately into the cylindrical stainless steel reaction chamber, which was maintained at 60 torr. The oxygen partial pressure was 30 Torr. 0 The substrates were heated resistively at 800 C. After growth, the films were cooled down at a rate of 5 °C/min under 1 The X-ray diffraction atmospheric pressure of pure oxygen. pattern of the films showed primarily an orientation of c-axis perpendicular to the substrates, with weak peaks of (hoo) Scanning Electron to a-axis orientation. corresponding Microscopy of the films showed a well-developed a-axis and caxis plate-like structure which appeared as rectangular micronsized features on the MgO surface. On the YSZ substrates a-axis and c-axis plate-like projections were also observed, with the Four probe dense plate-like c-axis orientation dominant. resistance measurements showed Tc(R=0) at 91.8 K(ATc=2.2 K) and 85 K (ATc=7 K) on YSZ and MgO substrates respectively. INTRODUCTION has been studied (YBCO) system[l] The Y-Ba-Cu-O extensively and superconducting thin films of these materials deposition techniques. have been fabricated by several These materials have received attention even though [2,3,4,5,6) this materials system has a lower transition temperature and more sensitive to the environment than Bi-and Tl-based The YBCO system has only one stable superconducting system. phase for superconductivity, whereas in the Bi-and Tl-system, there are many other stable superconducting phases.[7] In earlier works, post-annealing process temperatures over 900 oC were necessary before the film became superconducting. In order to be compatible with device fabrication, however, the superconducting films must be grown in-situ because the postannealed films always form rough surface and/or large grains. Also for device applications, ultra-thin films (-100-1500 A) should be able to be grown, but post-annealed films cannot achieve this because of the strong interaction with the substrate at those high temperatures. Mat. Res. Soc. Symp. Proc. Vol. 169. '1990 Materials Research Society
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Among many deposition techniques for superconducting thin films, metalorganic chemical vapor deposition (MOCVD) is an important technique fo
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