SPECTROSCOPIC STUDIES DURING PULSED-LASER ABLATION DEPOSITION OF C-N FILMS

Mass and optical emission spectra were recorded during XeCl laser abla tion of graphite targets in vacuo and in low pressure (up to 2.5 mbar) N-2 and NH3 atmospheres to study the role of gas phase reactions in C -N compound formation. Mass spectra were recorded during ablation in v acuo (10(-6) mbar) and in N-2 at 1 x 10(-4) mbar. In vacuo, during the first stage of ablation, the mass spectrum was characterized by the p eaks at 12 and 26 amu (C and CN). The CN peak intensity was slowly dec reasing with the laser pulse number, to disappear after similar to 300 0 laser pulses. In contrast, the peak at 26 amu is permanent during th e whole ablation when N-2 is introduced in the chamber. The optical em ission spectra recorded during ablation in vacuo are dominated by the bands of the C-2 Swan system. Weak bands from CN can also be distingui shed. Spectra recorded during ablation in NH3 are also dominated by th e bands of the C-2 Swan system. During ablation in N-2 (10(-4)-2.5 mba r), strong bands of the CN violet system are detected. Their intensiti es increase with increasing N-2 pressure and, at the same pressure, wi th increasing laser fluence. It was observed that the N atom density r ecorded in the deposited C-N films is increasing with the intensity of the CN emission.