High speed synthesis of diamond using in-liquid plasma

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1. High speed synthesis of diamondDiamond synthesis experiment was performed using in-liquid plasma process by changing experimental parameters (concentration of alcohol solution, substrate temperature, electric power and frequency, gap space between substrate and electrode). By increasing the pressure and the plasma power, the far higher growth rate was achieved than the conventional CVD diamond processes. Effective introduction of Microwave to electrode was also achieved. When the electric power of 300 W and 2.45 GHz microwave was irradiated into the methanol solution by the 6 mm electrode, the diamond film that has the thickness of 33 μm and width of 5 mm could be synthesized on the silicon substrate in 10 min. Growth rate was estimated as 200 μm/h. The result was submitted as a patent.2. Synthesis of silicon carbide (SiC)The good SiC crystals were synthesized by the chemical process that the hydrogen radicals pull up the impurity oxygen atoms contained in the forming SiC film. The graphite crystals were simultaneously synthesized between the SIC crystal grains. This chemical process was proved by the investigation of the plasma spectra.3. Synthesis of aluminum nitride (AIN)In-liquid plasma was generated in the water solution of AiCl_3 and NH_4X (X: anion) and AIN synthesis experiment was investigated. Alumina (Al_2O_3) could be synthesized; however, AIN could not be synthesized. It is important that the distance between aluminum and nitrogen atoms become closed when in-liquid plasma chemical reaction occurs.