C-2 SWAN BAND EMISSION INTENSITY AS A FUNCTION OF C-2 DENSITY

We report the systematic comparison of the optical emission intensity of the d(3) Pi --> a(3) Pi (0, 0) vibrational band of the C-2 Swan sys tem with the absolute C-2 concentration in Ar/H-2/CH4 and Ar/H-2/C-60 microwave plasmas used in the deposition of nanocrystalline diamond. T he absolute C-2 concentration is obtained using white-light absorption spectroscopy. Emission intensity correlates linearly with C-2 density for variations of several plasma parameters and across two decades of species concentration. Although optical emission intensity generally is not an accurate quantitative diagnostic for gas phase species conce ntrations, these results confirm the reliability of the (0,0) Swan ban d for relative determination of Cp density with high sensitivity under conditions used for hydrogen-deficient plasma-enhanced chemical vapou r deposition of diamond.