Optical emission spectroscopy study of the plasma plume produced by laser ablation of SiC in a nitrogen atmosphere

Optical emission spectroscopy experiments were carried out during the laser ablation of a polycrystalline Silicon Carbide target, both in vacuum and in presence of a controlled nitrogen atmosphere. Time integrated and spatially resolved emission spectra were dominated by the atomic emission lines from silicon and carbon species, either neutral or singly ionized. When the ablation process was carried out in a nitrogen gas background we found direct evidence of the formation of the CN molecular specie. Fast photography imaging of the expanding plume revealed the formation of a shock wave at a nitrogen pressure above 13.3 Pa, with the consequent heating of the shocked region and enhancement of the kinetics of ionization and excitation. A CN formation mechanism involving atomic carbon and nitrogen in presence of a shock wave is suggested.