Development of Transparent Diamond Plates Synthesis Apparatus by magnetic field assisted Arc Discharge Plasma Jet

采用适合于高速合成的弧光放电等离子体喷射化学气相沉积方法合成金刚石薄膜。然而，这种方法存在一些缺点，如金刚石板材的厚度分布和质量分布。为此，设计并研制了一种新型的利用磁场控制等离子体状态的装置。该装置由一个可沿等离子体炬轴线移动的电磁铁和一个等离子体射流组成。在由甲烷、氢气和Ar气体产生的电弧和等离子体射流中施加磁场后，等离子体射流的直径增大，衬底温度分布、厚度和质量在直径7-8 mm范围内得到改善。在较低的甲烷浓度为1%时，获得了透过率较高的金刚石薄膜，而与成核密度无关。用FTIR测试了用金刚石砂轮抛光后的金刚石片在10微米波长下的透过率约为68%。X射线衍射分析表明，该透明金刚石膜具有无规则的取向，通过对其横截面结构的观察，发现其缺陷和杂质较少。由于在所确定的沉积条件下合成厚的透明金刚石膜需要很长的时间，所以CVD设备需要产生稳定的、长寿命的等离子体射流。

Diamond films were synthesized by are discharge plasma jet CVD that is suitable for high rate synthesis. However, this method has drawbacks such as distributions of thickness and quality occurs in diamond plates. Thus, a newly type of an apparatus were designed and developed in order to control the plasma state by magnetic field. This apparatus were prepared an electromagnet movable along the axs of the plasma torch and a plasma jet. As a result of application of magnetic field to an arc and a plasma jet generated with methane, hydrogen and argon gases, the diameter of a plasma jet increases, and the distributions of the substrate temperature and the thickness and quality are improved in the range of 7-8 mm in diameter.The deposition conditions were also discussed for synthesizing transparent diamond plates. Diamond films that have high transmittance are obtained at lower methane concentration of 1% independently of nucleation density. Transmittance of the diamond plates that were polished with diamond wheel was measured with FTIR and was approximately 68% at the wavelength of 10 mum. This transparent diamond film was found to have random orientation by X-ray diffraction analysis and less defects and impurities by the observation of the structure of its cross section. Since it takes long time to synthesize thick transparent diamond films under the determined deposition conditions, CVD apparatuses need to generate a stable and long-life time plasma jet.