Detection of CN radicals in DC nitrogen plasma used for deposition of CN x layers

Abstract

Emission spectra from a DC plasma discharge of nitrogen with a graphite cathode used for deposition of CN x layers were investigated in the visible range 350–900 nm. The spectra recorded at low and high resolution from both the negative glow and the positive column of the discharge were studied separately. All spectra are dominated by neutral and ionised N 2 emission. In the positive column the violet band of the cyanogen (CN) radical was identified and analysed for vibrational structure. From a computer simulation of the rotationally resolved violet band, vibrational temperatures were derived and found to be in the intensity distribution for the v=0, 1 and 2 levels from thermal equilibrium. In the negative glow the strong N 2 + features completely mask the spectral region of the violet band of CN. Conclusions were drawn concerning the CN formation by chemical sputtering, and the role of CN radicals in the formation of polymeric CN x layers of 1:1=C:N stoichiometry.