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

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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.