Spectroscopic studies during pulsed laser ablation deposition of C-N films

Mass and optical emission spectra were recorded during XeCl laser ablation 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 vacuo (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 peaks at 12 and 26 amu (C and CN). The CN peak intensity was slowly decreasing with the laser pulse number, to disappear after similar to 3000 laser pulses. In contrast, the peak at 26 amu is permanent during the whole ablation when N-2 is introduced in the chamber. The optical emission spectra recorded during ablation in vacuo are dominated by the bands of the C-2 Swan system. Weak bands from CN can also be distinguished. Spectra recorded during ablation in NH3 are also dominated by the bands of the C-2 Swan system. During ablation in N-2 (10(-4)-2.5 mbar), strong bands of the CN violet system are detected. Their intensities increase with increasing N-2 pressure and, at the same pressure, with increasing laser fluence. It was observed that the N atom density recorded in the deposited C-N films is increasing with the intensity of the CN emission.