Preparation of YBaCuO Superconducting Thin Films by Microwave Plasma Enhanced OMCVD
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PREPARATION OF YBaCuO SUPERCONDUCTING THIN FILMS BY MICROWAVE PLASMA ENHANCED OMCVD KENJI EBIHARA*, TOMOAKI IKEGAMI*, SEIJI KANAZAWA-, AND MASANOBU SHIGA** *Kumamoto University, Dept. of Electrical Engineering and Computer Science, Kurokami 2-39-1, Kumamoto 860, Japan. **Dojindo Laboratories, Techno Research Park, Tabaru, Kamimashiki, Kumamoto 861-23, Japan. ABSTRACT A plasma-enhanced organometallic chemical vapor deposition (PE-OMCVD) has been studied as an alternative plasma process to prepare high Tc superconducting thin films. Metal 8 -diketonates such as Y(fod)3, Ba(hfa)2 and Cu(hfa)2 were decomposed by Ar/Oz plasmas produced with an applicator type microwave discharge system. Optical emission spectroscopy was used to monitor radical species during vaporization and decomposition of the source materials. The YBaCuO films grown on substrates(MgO, SrTiO3 and c-Si) showed amorphous structure. After the post-annealing, the films exhibited an x-ray diffraction pattern with c-axis perpendicular to the substrate and showed an onset superconducting transition temperature of 87 K. The PE-OMCVD process provided high film deposition rate of 30-120 nm/min. INTRODUCTION Electronic application of high Tc superconductors requires stoichiometric, well crystallized and thin-film structures. To date, superconducting films have been prepared by various techniques such as electron beam evaporation or coevaporation, laser ablation, magnetron sputtering, molecular beam epitaxy and organometallic chemical vapor deposition (OMCVD). OMCVD has the advantages of high deposition rates, low substrate temperature, easy control of the film composition and amenability to large scale processing. The use of a plasma in the OMCVD process offers potential improvements in optimum decomposition, lowtemperature deposition, high growth rate, reactant incorporation. Recently, the plasma-enhanced organometallic chemical vapor deposition (PE-OMCVD) process has been attempted to form high Tc superconducting thin films. Bai et al. prepared thin films of high Tc superconducting YBaCu metal oxide using 6 diketonate chelates, Y(dpm)3, Ba(dpm)2 and Cu(dpm)z as the metalorganic precursors[l]. In their reaction chamber was a pair of capacitor plates which were connected to an rf(13.56 MHz) generator. Kobayashi et al. reported the preparation of superconducting BiSrCaCuO films by the PE-OMCVD method[2]. The plasma was generated by applying rf(13.56 MHz) power to a coil surrounding a quartz reactor. We report here a microwave plasma enhanced chemical vapor deposition process for preparation of high Tc superconducting YBaCuO thin films. Optical emission spectroscopy was used to monitor the decomposition of the source materials. The structure of the films was analyzed by using x-ray diffraction and the surface morphology was examined by scanning electron microscopy (SEM). The composition of the films was checked by using the electron probe microanalysis(EPMA). Mat. Res. Soc. Symp. Proc. Vol. 190. 01991 Materials Research Society
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EXPERIMENT The schematic diag
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