Analyses of gas-phase reactions during reactive laser ablation using emission spectroscopy

Time- and space-resolved emission spectroscopic measurements have been performed to investigate the formation of molecular species in the plasma plume generated by pulsed-laser ablation of Al, C and Ti targets in either N-2 or O-2 low-pressure atmospheres. The recorded spectra show that the interaction between the vapour plume and the ambient gas gives rise to the partial dissociation and ionization of the ambient gas and that the formation of nitride or oxide diatomics depends strongly on the binding energies of these species with respect to dissociation potential of the gas molecules. Thus, nitride formation in the gas phase occurred only during carbon ablation while oxide molecules were detected in the plasma plume originating from every target material. The influence of the atomic mass of the target material on the gas-phase reactions is also discussed. The results contribute to a better understanding of the mechanisms involved in the thin-him synthesis by reactive pulsed laser deposition.