In-Situ Preparation and Characterization of Superconducting Thin Films and Related Materials by Mocvd for the Developmen
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IN-SITU PREPARATION AND CHARACTERIZATION OF SUPERCONDUCTING THIN FILMS AND RELATED MATERIALS BY MOCVD FOR THE DEVELOPMENT OF THREE TERMINAL SWITCHING DEVICES R. Singh, S. Sinha, and J. Narayan* School of Electrical Engineering and Computer Science, University of Oklahoma, Norman, OK 73019 *Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7916 ABSTRACT Metalorganic chemical vapor deposition (MOCVD) has the potential of emerging as a major technique for the fabrication of high temperature superconductor devices. In this paper, we present preliminary results of in-situ deposition of Y-Ba-Cu-O thin films (T,- = 79K) by rapid isothermal processing assisted MOCVD on BaF 2 /silicon substrates. INTRODUCTION Realization of a three terminal switching device based on high temperature superconductors will be a giant step forward in superconducting electronics, making possible designs at the chip level much like those now used with semiconductors. Such devices would have switching times of the order of 100 fs and will open the door to several novel applications. For thin film applications, metal organic chemical vapor deposition (MOCVD) can play a major role in the realization of three terminal switching devices as well as other similar devices. Thus, MOCVD in addition to well established roles in semiconductor and optoelectronics industry can play a similar role in the superconductor industry. The primary objective of this paper is to present our preliminary results on the deposition and characterization of Y-Ba-Cu-O (YBCO) and related materials deposited on Si substrates by rapid isothermal processing (RIP) assisted MOCVD. EXPERIMENTAL PROCEDURES The horizontal reactor was designed to handle extremely low vapor pressure precursors. Ultra high purity argon was used as a carrier gas to transport vapors of the organometallic precursors.
These were then mixed in a heated manifold with oxy-
gen before entering the reactor. Hexafluoroacetylacetonate of barium was used as the source for deposition of BaF 2 films [1]. The source oven temperature was maintained at 230'C and the reactor pressure
-
5 Torr. Substrates used were (100) and (111)
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silicon. In some cases thin layers of BaF 2 were deposited by using solid phase epitaxial approach [2]. For the YBCO film deposition, 2,2,6,6-tetramethyl-3, 5-heptanedionates (TMHD) of Y, Ba, and Cu were used as the precursors. However, the Ba (TMHD) 2 partially decomposes during the vaporization process and consequently there is poor transport of barium. This problem was overcome by passing vapors of a mixture of hydrogen (TMHD) and tetrahydrofuran (THF) over the Ba source. The source oven temperatures were 160, 270, and 160'C for Y, Ba, and Cu respectively. Substrate heating was done by tungsten halogen lamps. Substrate temperature was 800'C during deposition, with
"agradual cool down to room temperature in a low pressure oxygen environment over "aperiod of one ho
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