Preparation and characterization of electrochemically deposited carbon nitride films on silicon substrate

Carbon nitride films (CNx films) were deposited on Si(100) substrates by the electrolysis of methanol–urea solution at high voltage, atmospheric pressure, and low temperature. The microstructure and morphology of the resulting CNx films were analysed by means of Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectrometry (FTIR), x-ray diffraction (XRD), and atomic force microscopy. The tribological properties of the CNx films were examined on an UMT-2MT friction and wear test rig. The Raman spectrum showed two characteristic bands: a graphite G band and a disordered D band of carbon, which suggested the presence of an amorphous carbon matrix. XPS and FTIR measurements suggested the existence of both single and double carbon-nitride bonds in the film and the hydrogenation of the carbon nitride phase. The XRD spectrum showed various peaks of different d values, which could confirm the existence of the polycrystalline carbon nitride phase. The hydrogenated CNx films were compact and uniform, with a root mean square roughness of about 18 nm. The films showed excellent friction-reduction and wear-resistance, with the friction coefficient in the stable phase being about 0.08. In addition, the growth mechanism of the CNx films in liquid phase electro-deposition was discussed as well. It was assumed that the molecules of CH3OH and CO(NH2)2 were polarized under high electric field, and the CNx film was formed on the substrate through the reaction of the –CH3 and –NH2 groups on the cathode.