Low voltage electrodeposition of CNx films and study of the effect of the deposition voltage on bonding configurations

Carbon nitride (CNx) films were deposited from acetonitrile at low voltage (150-450 V) through electrodeposition. The films were characterized by atomic force microscopy (AFM), Raman spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. AFM investigations revealed that the grain size was ∼200 nm and roughness was ∼10 nm. The films were found to be continuous and close packed. IR spectra revealed existence of strong sp3, sp2 type bonding and weak sp type carbon nitrogen bonds and these bonds were found to increase with voltage. The fraction of sp3-bonded species in the sample increased in low voltage range and after reaching maximum at 350 V, decreased for higher voltages. However, the concentration of sp2 CN ring structures in the film increased with increasing voltage. Also, the peak width decreased at low voltages reaching a minimum and increased thereafter. It was observed that the voltage dependent increase in the concentration of polymeric type sp2 CN (chain) structures was much more pronounced than that of graphitic type sp2 CN (ring) structures. Raman spectra showed the presence of both the D and G bands. The shift in the G band indicated the presence of nitrogen in the film. The ID/IG ratio was found to increase with the incorporation of nitrogen. Auger electron spectroscopy (AES) showed a clear increase in the nitrogen content with increase in the voltage. The formation of the film could be explained on the basis of dissociation of electrolyte under applied voltage.