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

Abstract
To study the characteristics of the plasma plume generated by KrF excimer laser irradiation of graphite, optical emission spectra (OES) of plasma species have been recorded for different distances from the target and for various ammonia pressures. The laser fluence and the ammonia pressures were set to values typically applied during the deposition of carbon nitride thin films. Emission spectra of CN, CH and NH radicals were recorded as a function of time for different deposition conditions. The experimental vibration-rotation bands were fitted to a synthetic spectrum of CN, CH and NH radicals. Rotational and vibrational temperatures deduced from the analysis of CN emission spectra were found to be equal, indicating that a collisional equilibrium was reached among the heavy particles of the plasma plume. Comparison of rotational and vibrational temperatures deduced from the spectra recorded in nitrogen atmosphere is also presented.

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