Bias Effect on the Formation of Carbon Films by RF-Plasma CVD

This paper is concerned with the bias effect of additional DC voltage, which is applied between the reaction chamber and the substrate, on the properties of carbon films prepared by RF-plasma CVD. Hard carbon films (Hv≤2500) of 50-100nm thick were synthesized by the plasma CVD method with negative DC voltage to the substrate. The deposition rate, refractive index and microhardness of the films increased with increasing negative voltage at -140V or above. Their Raman spectra showed two broad peaks at 1350cm-1 and 1550-1580cm-1. These facts suggested that the additional negative bias promoted the formation of i-carbon and/or diamond like structures in the films.