Role of Nitrogen in the Formation of $\hbox {CN}_{x}$ Films by Pulsed Laser Deposition

Carbon nitride (CN_x) films, deposited by pulsed laser deposition (PLD) in nitrogen (N₂) atmosphere, were studied with respect to mechanical, morphological, compositional, structural, and optical properties. All the samples were prepared at room temperature and under various N₂ pressures, ranging from vacuum up to 50 Pa. Nitrogen concentration ( C_N) rapidly increases with increasing N₂ pressure and reaches to a saturated value above 10 Pa. The Raman results reveal that the D/G ratio increases with the increase in N₂ pressure, contributing the graphitization of carbon films. With further addition of nitrogen into carbon films, optical transmission is enhanced. Localization of the electrons due to the heteropolar bonding and the high porosity of the CN_x samples are speculated to be the reason of enhancement in optical transmission.