Development of large-area Diamond Film Synthesis Apparatus by Chemical Vapor Deposition using Arc Discharge Plasma

为了扩大弧光放电等离子体喷射化学气相沉积金刚石的沉积面积，研制了一种由一个阴极等离子体炬和三个阳极等离子体炬组成的新型装置。这四个等离子体炬可以沿着各自的轴向移动，放电区域随着等离子体炬排列的变化而变化。在本研究中，讨论了利用该装置扩大金刚石沉积面积的可能性，并对合成的金刚石膜的生长速度、膜的形状和性能进行了评价。此外，还对金刚石膜的力学性能进行了表征，采用了激光切割金刚石膜和热化学反应抛光金刚石膜的方法，在气压为200Torr、甲烷浓度为4%的条件下，随着放电面积的增大，金刚石沉积区直径增大，达到40 mm。增大垂直于等离子体射流轴线方向的放电距离对扩大金刚石沉积面积更为有效。随着出土距离的增加，活性物种的数量增加，生长速率也随之提高。然而，当放电距离改变时，中心部分较厚的膜的形状没有改变。此外，用拉曼光谱对金刚石膜的结晶度进行了表征，结果表明，金刚石膜的结晶度与等离子体炬的排列无关，金刚石膜已被加工成刃口，并对铝合金进行了切割。实验结果表明，该CVD金刚石膜可用于超精密刀具，并具有与天然金刚石相同的机械强度。

In order to enlarge the diamond deposition area by arc discharge plasma jet chemical vapor deposition, a newly type of apparatus that has one cathode plasma torch and three anode plasma torches has been developed. These four plasma torch can be moved along their own axs, discharge area is changeable with changing the arrangement of the plasma torches. In this research, the possibility of the enlargement of the diamond deposition area by this appatatus has been discussed, and the growth rate, the film shape and properties of synthesized diamond films have been evaluated. Moreover, the mechanical properties of the diamond film has been characterized by applying the diamond film for cutting tool that was mode by YAG laser cutting technique and polishing technique by heat-chemical reaction with hot metal plate.As a result, the diamond deposition area has been enharged at up to 40mm in diameter with increasing the discharge area when the pressure has been 200 Torr and methane concentration has been 4%. It is more effective for enlargement of the diamond deposition area to increase the discharge distance in the direction that is perpendicular to the axis of the plasma jet. The growth rate has been incerased with increasing the dischaege distance because the number of active species has increased. However, the film shape that central part is thicker has not changed when the discharge distance has been varied. Moreover, the crystallinity of the diamond film was characterized by Raman spectroscopy and it has been found that good crystallinity has been obtained independent of the arrangement of the plasma torches.The diamond film has been shaped into a cutting edge and cutting of aluminum alloy was performed. The result of the experiments shows that the this CVD diamond film can be usued for ultraresicion cutting tool and has the same mechanical strength as natural diamond.