Formation of diatomic molecular radicals in reactive nitrogen-carbon plasma generated by electron cyclotron resonance discharge and pulsed laser ablation

Abstract

The reactive nitrogen-carbon plasma generated by electron cyclotron resonance (ECR) microwave discharge of N2 gas and pulsed laser ablation of a graphite target was characterized spectroscopically by time-integrated and time-resolved optical emission spectroscopy with space resolution for a study of gas-phase reactions and molecular radical formation in the plasma. The plasma exhibits very high reactivity compared with the plasma generated solely by ECR discharge or by pulsed laser ablation and contains highly excited species originally present in the ambient gaseous environment and directly ablated from the target as well as formed as the products of gas-phase reactions occurring in the plasma. The space distribution and the time evolution of the plasma emission give an access to the gas-phase reactions for the formation of C2 and CN radicals, revealing that C2 radicals are formed mainly in the region near the target while CN radicals can be formed in a much larger region not only in the vicinity of the target, but especially in the region near a substrate far away from the target.