Estimation of chemical sputtering rates of carbon in He-H2 glow discharge plasmas by optical emission spectroscopy

The sputtering of cathode plates in glow discharge plasma with He-H2 gas mixtures has been investigated. The sputtering rate of the carbon plate alone increased with increasing H2 pressure. This enhancement in the sputtering rate of carbon can be explained by chemical sputtering with H+ ions dissociated from H2 molecules. The dependence of optical emission intensities of CH and C2 molecules on H2 pressure was very similar to that of the sputtering rate of carbon. Thus, correlation between the sputtering rate of carbon and the optical emission intensity was investigated. It has been found that the correlation between the sputtering rate of carbon and the intensity ratio I(CH 431.4 nm)/I(He I 501.6 nm) gave the best correlation coefficient. Therefore, it is possible to estimate the chemical sputtering rate of carbon by monitoring the emission intensities of CH 431.4 nm and He I 501.6 nm. (author)