Sumitomo Electric Industries, Limited

Takayuki Shibata

Naoji Fujimori

Nobuhiro Ota

Takahiro Imai

Akihiko Ikegaya

Diamond having a large coefficient of thermal conductivity is prepared by a CVD method in which a reaction gas is decomposed and reacted under such condition that a concentration of carbon atoms in relation to hydrogen gas (A %), a concentration of nitrogen gas in relation to the whole reaction gas (B ppm) and a concentration of oxygen atoms in relation to the hydrogen gas (C %) satisfy the equation:

Chemical vapor deposition method of high quality diamond

A diamond film deposited on a substrate heated at less than 400.degree. C. in vapor phase from material gas including hydrogen gas and hydrocarbon gas often incurs low strength, low abrasion resistance, and opacity owing to high concentration of non-diamond ingredients. The inventors have discovered that inclusion of nitrogen gas in material gas is likely to raise the concentration of non-diamond ingredients. Good diamond film of good quality shall be obtained by synthesizing from the material gas in which the nitrogen concentration is less than 1000 ppm. The smaller the nitrogen concentration is suppressed, the higher the quality of diamond rises.

Low temperature method for synthesizing diamond with high quality by

A diamond synthesizing method introduces a mixed gas of hydrocarbon gas and hydrogen gas into a reaction vessel (9) which is maintained under a pressure of 1 to 100 Torr. A dc discharge is caused across a cathode (1) and an anode (2), thereby depositing diamond on a substrate (3) which is placed on the anode (2). A positive column of H.alpha.&gt;CH is produced with a high formation rate of atomic hydrogen for promoting decomposition of the hydrocarbon gas, and the concentration of hydrocarbon is reduced while maintaining the condition. According to this method, it is possible to synthesize high-quality diamond, which hardly any non-diamond carbon components such as amorphous carbon and graphite, at a film forming rate of about 1 .mu.m/h.

Growing community of inventors

Otaru, Japan

Takayuki Shibata