High speed synthesis of diamond using in-liquid plasma

1.金刚石的高速合成通过改变实验参数（乙醇溶液浓度、基片温度、电功率和频率、基片与电极之间的间隙），利用液相等离子体技术进行了金刚石的高速合成实验。通过增加压力和等离子体功率，实现了比常规CVD金刚石工艺高得多的生长速率。同时实现了微波对电极的有效导入。当微波功率为300 W，频率为2.45 GHz，电极直径为6 mm时，在10 min内就可以在硅衬底上生长出厚度为33 μm，宽度为5 mm的金刚石薄膜，生长速率为200 μm/h。该成果已作为专利提交。碳化硅（SiC）的合成通过氢自由基提拉SiC薄膜中的杂质氧原子的化学过程，合成出质量较好的SiC晶体。在SiC晶粒之间同时合成石墨晶体。等离子体光谱的研究证实了这一化学过程.在AlCl_3和NH_4X（X：阴离子）的水溶液中产生液相等离子体，进行了氮化铝（AlN）的合成实验。可以合成Al_2O_3，但不能合成AlN。重要的是，当发生液体中等离子体化学反应时，铝原子和氮原子之间的距离变得接近。

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.