Diamond Synthesis From Acetone Vapor And Impurity Control
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Diamond Synthesis From Acetone Vapor And Impurity Control Kaoru Gyoda, Yuki Tanaka, Yoshiki Takagi Teikyo University of Science & Technology, 2525, Yatsusawa, Uenohara-machi, Kitatsuru-gun, Yamanashi-Pref., 409-0193, JAPAN. ABSTRACT We synthesized diamond via gaseous phase of vaporized acetone. Molecular acetone decomposes to two methyl radicals with thermal activation. We propose here a new method for diamond synthesis with these methyl radicals from molecular acetone. With this method, we successfully synthesized diamond particles on Si substrates with shorter experimental time and lower energy consumption than conventional methods. With liquid carbon sources, such as acetone, impurity elements will be easily substituted in synthesized diamond thin film, which has wide applications for the future electronic devices. Nickel, Boron and Phosphorus doping results will be presented. INTRODUCTION The conventional techniques for depositing diamond at low pressure utilize a flow of a hydrocarbon-hydrogen gas mixture [1] with complicated gas line to introduce reaction gas into a reaction chamber and evacuating reactant gas from it. Beside that, these techniques require a complicated method for generation of atomic hydrogen, such as a plasma [2], hot tungsten filament [3,4], or flame [5]. Therefore, these types of flow systems are considered to be impracticable for mounting on a spacecraft. For few years, we had been concentrated on developing completely closed diamond synthesizing system aimed for microgravity conditions [6-9]. Recently we started the new method with graphite heater as carbon source [10,11]. With this method a completely closed system is achieved. At the same time, we started other new method with liquid carbon sources. With this method, pseudo-closed system is performed. In this paper, experimental results with liquid carbon sources will be presented. In-situ analysis of gaseous species in a reaction chamber by using gas chromatography and possible reaction model is reported elsewhere [12, 13] K. Fabisiak et al. reported diamond synthesis on various substrates [14]. They used thermal filament method with acetone and hydrogen mixture gas flow system. Okoshi et al.
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synthesized diamond-like carbon from laser abrasion with frozen acetone [15]. One acetone molecule has two methyl groups, which has very important role on diamond synthesis with gaseous reactions. Acetone molecule reacts with hydrogen molecules and produces two methane molecules and one carbon mono-oxide. EXPERMENTAL We used liquid carbon source, such as acetone, methanol, ethanol, ethylene glycol and tertiary butyl alcohol. One molecule of these five liquid carbon sources has 2, 1, 2, 2, and 4 methyl groups, respectively. So it is expected that diamond will be synthesized with relatively low activation energy consumption. Reaction apparatus is shown in Fig.1.Tungsten filament was set perpendicular to the substrate on the center of the reaction chamber. After air was evacuated from the chamber, the liquid carbon source was int
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