Nano Crystalline Diamond Synthesized by Hot Filament Chemical Vapor Deposition
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0956-J09-38
Nano Crystalline Diamond Synthesized by Hot Filament Chemical Vapor Deposition Takayuki Hirai1, Yoshinori Kanno1, and Yoshiki Takagi2 1 University of Yamanashi, 4-4-37 Takeda, Kofu, 400-8510, Japan 2 Teikyo University of Science & Technology, 2525 Yatsusawa, Uenohara, 409-0193, Japan
ABSTRACT Due to its extreme hardness, chemical and mechanical stability, large band gap and highest thermal conductivity, a poly-crystalline diamond is expected to be an excellent packaging material for biomedical and environmental MEMS devices. Recently nano crystalline diamond (NCD) has been synthesized by microwave plasma chemical vapor deposition (MPCVD) technique using a gas mixture of methane-hydrogen or methane-hydrogen and inert gas, argon mixture. Diamond synthesis from liquid carbon source has a relatively high growth rate among various CVD methods. Hot filament chemical vapor deposition (HFCVD) is popular method in order to grow the diamond particles or films. The equipment of HFCVD in present paper is simple and easy to operate. Therefore we tried to NCD synthesis by HFCVD from liquid carbon source such as methanol, ethanol etc. The structure, surface morphology, and grain size of the diamond were examined with field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy. We confirmed our diamond particles as NCD with typical Raman peak of NCD. And we observed 100nm under in diameter with FE-SEM. We will refer to NCD films synthesis by HFCVD in the paper.
INTRODUCTION Diamond is a promising material for various types of electronic micro- or nano-fabricated electron device [1], because of its wide-bandgap, high carrier transport mobility, high breakdown field and negative electron affinity. Recently, there is a wide interest in improving the electron field emission properties of diamond films. One of the possible routes for increasing the electron field emission capacity of diamond films is to reduce the grain size [2]. The other possible route is to increase the enhancement factor by increasing the emitter’s aspect ratio [3]. However, high hardness and chemical inertness of nano diamond makes it difficult to form arbitrary shapes [4]. The diamond particles or films were synthesized with HFCVD in present paper. We used liquid carbon source and hydrogen mixture in equipment. Then we tried to control water concentration ratio in liquid ethanol. To clarify the water concentration effect on diamond particle morphology, shape and size. In this paper, diamond film and isolated diamond particle were studied in liquid carbon source of ethanol with HFCVD.
EXPERIMENTAL DETAILS First, the suitable working concentration of water into the ethanol was prepared. The commercial ethanol includes a slight amount of water, so we tried to dehydrate of ethanol. And high-purified water doped to 0.5%, 1.0%, 5.0%, 10.0% and 20.0% to ethanol. We used ethanol as liquid carbon source. Substrates were silicon single crystal with p-type(100) with 10 x 30 mm2 in size. And substrates surface were scratched by diamond powder
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