Low Temperature Growth of Diamond Films from Vapor Phase

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The synthesis of diamond films from ethyl alcohol and hydrogen was performed objecting to synthesize them at temperature as low as possible. We used a capacitively coupled rf (13.56 MHz) plasma CVD apparatus and an external heater. The films were prepared at various conditions varying gas pressure, gas concentration, heating temperature and electorode distance. The films were characterized by Raman scattering, SEM and ESR, and the following results were obtained.1. When a reaction tube with a diameter of 50 mm is used, diamond films do not grow if the tube is not heated. This is due to that the temperature produced by only rf discharge is not sufficient for diamond growth.2. When the temperature is set at 550ﾟC by an electric furnace, diamonds grow at gas pressures of 1 - 3 Torr and ethyl alcohol concentrations of 1 - 3 %.3. Under above pressure and concentration, diamonds grow at temperatures of 350 - 800ﾟC.4. The films grown at 350ﾟC contain nondiamond components in addition to diamonds. They are composed of balllike particles.5. When a reaction tube with a diameter of 35 mm and an infrared heater are used, the film of high quality is obtained by optimizing the electrode distance.6. In above case, the film without nondiamond components is obtained even without the heating. The temperature in this case is estimated to be 370ﾟC.