Low Temperature Preparation of Y-Ba-Cu-0 High Tc Superconducting Thin Films by Plasma-Enhanced Organometallic Chemical V
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LOW TEMPERATURE PREPARATION OF Y-Ba-Cu-O HIGH Tc SUPERCONDUCTING THIN FILMS BY PLASMA-ENHANCED ORGANOMETALLIC CHEMICAL VAPOR DEPOSITION JING ZHAOa,b), HENRY 0. MARCYC), LAUREN M. TONGEd), BRUCE W. WESSELSa,e), TOBIN J. MARKSd,e) AND CARL R. KANNEWURFc,e) a)Department of Materials Science and Engineering b)Current address: EMCORE Co., 35 Elizabeth Ave., Somerset, NJ 08873 C)Department of Electrical Engineering and Computer Science d)Department of Chemistry e)Authors to whom correspondence should be addressed. Materials Research Center, Northwestern University, Evanston, IL 60208 ABSTRACT We report here a plasma-enhanced organometallic chemical vapor deposition process for the preparation of YBa2Cu3O7-x thin films using two rf plasma coupling configurations. For the films grown under a direct plasma glow, the YBa2Cu3O7-x phase is not found in the as-deposited state. However, by employing plasmaactivated nitrous oxide as the reactant gas, superconducting YBa2Cu3O7-x films having a low carbon content and a mirror-like surface have been prepared in-situ at a substrate temperature of 6100C using an organometallic chemical vapor deposition process. INTRUDUCTION Prospects for early applications of copper oxide-based ceramics with superconductivity above liquid nitrogen temperature are most likely in the area of device applications, which critically depend on the feasibility of fabricating thin films with desired properties. Plasma-enhanced organometallic chemical vapor deposition (PE-OMCVD) is an attractive CVD approach to thin film formation which substitutes plasma energy for conventional thermal energy, and consequently offers the possibility of low temperature deposition, non-equilibrium film compositions, and high product purity. In this paper we report our preliminary results on the successful growth of YBa2Cu3O7-x films by PE-OMCVD. Mirror-smooth, high purity YBa2Cu3O7-x films have been prepared at a substrate temperature of 610 0 C by an OMCVD process without post anneal. PE-OMCVD was carried out in a modified system described elsewhere [1] having a horizontal quartz reactor with three separate parallel quartz inlet tubes for the introduction of the precursors. Purified 1-diketonate complexes Y(dpm)3, Ba(dpm)2 (dpm = dipivaloymethanate), and Cu(acac)2 (acac = acetylacetonate) were used as yttrium, barium, and copper precursors, respectively. The solid sources were maintained at 100, 150, and 250 0 C for Y(dpm)3 , Cu(acac)2, and Ba(dpm)2, respectively. The graphite susceptor upon which the substrate was placed was heated by an infrared lamp. Deposition was carried out at a system pressure of 3 torr with an argon gas flow (450 cc/min) transporting each precursor to the substrate region. The reactant gases oxygen and nitrous oxide were introduced into the reaction area through a separate tube with a Mat. Res. Soc. Symp. Proc. Vol. 169. @1990 Materials Research Society
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flow rate of -150cc/min. A plasma glow was generated using a parallel plate capacitor which surrounded the reactor wall and was powered by a 13.5
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