Diamond synthesis on oxide substrates
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Diamond synthesis on oxide substrates Rie Hayashi, Fumitomo Onishi and Yoshiki Takagi Teikyo University of Science and Technology 2525 Yatsusawa, Uenohara-machi, Kitatsuru-gun, Yamanashi pref., 409-0193 JAPAN ABSTRACT Recently, many results were reported by many institutes and companies all over the world for diamond particles or thin films synthesized on crystalline substrates, such as molybdenum, silicon etc. But diamond on amorphous or oxide substrates, were rarely reported. In this study, we used material of amorphous and oxide for substrates, for example quartz glass, Alumina. We used unique apparatus of diamond synthesis. With our apparatus, completely closed system was used, no reaction gas was introduced to the chamber and no reactant gas was evacuated from it. We used graphite rod for heater and carbon source, at the same time. And we compared results with this unique closed system and with conventional flow system. Carbon sources of gaseous state (methane) and solid state ( graphite ), and closed and flow system result the deference of synthesized diamond particles. INTRODUCTION With diamond synthesis, crystalline substrates, such as Si and Mo are usually used. In this study, we used oxide amorphous for example, quartz glass, and crystalline oxide such as aluminum oxide for substrates. In last year, on MRS Spring meeting, we reported the synthesized diamond on quartz glass[1]. In this study, we tried synthesis with conventional flow system and with methane and hydrogen mixture gas. EXPERIMENTAL In this study, we tried three deferent methods listed on Table 1. For each method, schematic figures are shown in Fig. 1. Method A is so called completely closed system. After hydrogen was introduced on the chamber with suitable pressure, all valves were closed, and graphite rod was heated up with electricity. To keep suitable temperature of graphite rod and substrate, which was heated with strong radiation come from graphite rod, diamond particles were synthesized on the substrates. Method B is flow system with graphite rod, which installed on the center of the chamber. Reaction gas (hydrogen) was introduced and reactant gas was evacuated to keep suitable pressure.
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Table 1 Experimental method
gas flow carbon source
A
B
C
closed system graphite rod
flow system graphite rod
flow system CH4 gas
Method C is common and conventional thermal filament method. For reaction gas, mixture of hydrogen and methane was used. For filament, spiral shaped tungsten wire was used. Experimental conditions were listed on Table 2. The synthesized particles were shown in Fig. 2, for Method A, Fig.3 (method B) and Fig.4 (C), with SEM photographs and Raman spectra.
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A B Figure 1. Schematic figure of apparatus for method A, B and C.
C
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