Uniform Growth of Nano-crystalline Diamond Thin Films by DC-glow Discharge CVD

The nano-crystalline diamond thin films with grain size ranging from 20 nm to 40 nm were synthesized on 2 inch silicon wafer by direct current glow discharge chemical vapor deposition (DCGDCVD). The working gas composited by H_2,CH_4 and Ar. The morphology and structure characteristics of diamond films impacted by different concentrations of CH_4 and Ar were observed by field-emission scanning electron microscope (FESEM),Raman spectroscopy and micro friction testing machine. The result shows that the grain size will refine as the CH_4 concentration increasing. However,massive graphite phase would generate at the atmosphere of excess CH_4. In addition,the doping of Ar could also improve the refining as the CH_4 concentration increasing,whereas it was at the cost of low film quality. Under optimal parameters,the smallest friction coefficient of NCD thin films could reach 0.12 and the largest deposition diameter of NCD thin films is 140 mm