Raman and infrared modes of hydrogenated amorphous carbon nitride

Features in the Raman and infrared (IR) spectra of highly ${\mathrm{sp}}^3$ bonded hydrogenated amorphous carbon nitride films are assigned. The Raman spectra show three main features all found in $\mathrm{a-}\mathrm{C}$ itself, the G and D peaks at 1550 and 1350 cm⁻¹, respectively, and the L peak near 700 cm⁻¹. The intensity ratio of the D and G peaks, $\mathrm{I(D)/I(G),}$ is found to scale as (band gap)⁻², which confirms that nitrogen induces carbon to form ${\mathrm{sp}}^2$ graphitic clusters. The intensity of the L mode is found to scale with the D mode, supporting its identification as an in-plane rotational mode of sixfold rings in graphitic clusters. A small feature at 2200 cm⁻¹ due to C≡N modes is seen, but otherwise the Raman spectra resembles that of $\mathrm{a-}\mathrm{C}$ and shows no specific features due to N atoms. The hydrogen content is found to have a strong effect on the IR spectra at 1100–1600 cm⁻¹ making this band asymmetric towards the 1600 cm⁻¹ region.