MEASUREMENTS OF THE GAS KINETIC TEMPERATURE IN A CH4-H2 DISCHARGE DURING THE GROWTH OF DIAMOND

Experiments to study the gas kinetic temperature in a dc hollow cathode discharge have been carried out under conditions suitable for diamond growth using CH4-H2 mixtures as the feed gas. The gas kinetic temperature is shown to be equal to the rotational temperature for particular emission bands in H-2 and in CN in a CH4-H2 discharge containing a small N2 impurity for total pressures above 10 Torr. The gas temperature can be obtained by measuring relative line intensities in emission of either the R branch of the G 1-SIGMA-g+ --> B 1-SIGMA-u+(0-0) band of H-2 or the R branch of the B 2-SIGMA+ --> X 2-SIGMA+(0-0) band of CN. The (0-0) symbol represents a band of transitions occurring between the levels with 0 vibrational quantum number in the upper electronic state and the levels with 0 vibrational quantum number in the lower electronic state. These measurements of gas kinetic temperature in a CH4-H2 discharge using optical emission spectroscopy have been confirmed by two different experiments using laser-induced fluorescence.