Role of nitrogen in the formation of CN _x films by pulsed laser deposition

Carbon nitride (CN _x) films, deposited by pulsed laser deposition (PLD) in nitrogen (N ₂) atmosphere, were studied with respect to mechanical, morphological, compositional, structural, and optical properties. All the samples were prepared at room temperature and under various N ₂ pressures, ranging from vacuum up to 50 Pa. Nitrogen concentration (C _N) rapidly increases with increasing N ₂ pressure and reaches to a saturated value above 10 Pa. The Raman results reveal that the D/G ratio increases with the increase in N ₂ pressure, contributing the graphitization of carbon films. With further addition of nitrogen into carbon films, optical transmission is enhanced. Localization of the π 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.