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

Carbon nitride
$(\hbox{CN}_{x})$
films, deposited by pulsed laser deposition (PLD) in nitrogen
$(\hbox{N}_{2})$
atmosphere, were studied with respect to mechanical, morphological, compositional, structural, and optical properties. All the samples were prepared at room temperature and under various
$\hbox{N}_{2}$
pressures, ranging from vacuum up to 50 Pa. Nitrogen concentration
$( \hbox{C}_{\rm N})$
rapidly increases with increasing
$ \hbox{N}_{2}$
pressure and reaches to a saturated value above 10 Pa. The Raman results reveal that the
$D/\hbox{G}$
ratio increases with the increase in
$\hbox{N}_{2}$
pressure, contributing the graphitization of carbon films. With further addition of nitrogen into carbon films, optical transmission is enhanced. Localization of the
$\pi$
electrons due to the heteropolar bonding and the high porosity of the
$\hbox{CN}_{x}$
samples are speculated to be the reason of enhancement in optical transmission.