A study of molecule formation during laser ablation of graphite in low-pressure ammonia

To study the characteristics of the plasma plume generated by KrF excimer l aser irradiation of graphite, optical emission spectra (OES) of plasma spec ies have been recorded for different distances from the target and for vari ous ammonia pressures. The laser fluence and the ammonia pressures were set to values typically applied during the deposition of carbon nitride thin f ilms. Emission spectra of CN, CH and NH radicals were recorded as a functio n of time for different deposition conditions. The experimental vibration-r otation bands were fitted to a synthetic spectrum of CN, CH and NH radicals . Rotational and vibrational temperatures deduced from the analysis of CN e mission spectra were found to be equal, indicating that a collisional equil ibrium was reached among the heavy particles of the plasma plume. Compariso n of rotational and vibrational temperatures deduced from the spectra recor ded in nitrogen atmosphere is also presented.