Dependence of the physical properties DLC films by PECVD on the Ar gas addition

Diamond like carbon films have been deposited using CH4/Ar gas mixtures with various CH4 concentrations by the rf-plasma enhancement chemical vapor deposition technique. It has been found that the deposition rate initially increases with the Ar dilution, but finally drops due to the pronounced etching effect of Ar ion sputtering and the reduced amount of CH4 present to sustain the growth of the films. The hardness and the integrated intensity ratio (I-D/I-G) of the Raman D-line and G-line, respectively, tend to increase with increase in the Ar fraction in the precursor gas mixture. FTIR spectra show that the amount of hydrogen in the films decreases with increasing Ar dilution. This may be due to the small amount of carbon-supplying gas (CH4) at a high Ar fraction and disruption of weak sp(2) CHn bonds by Ar ions. All these results show that the sp(3) fraction in the films increases with an increase in the Ar fraction in the precursor.