Effect of bombarding energy of N ions on composition, hardness and surface free energy of carbon nitride films

Carbon nitride (CNx) films were synthesized on silicon substrates by ion beam assisted deposition. Effect of bombarding energy of N ions on the properties of the CNx films was studied. Surface morphology and bonding states of the CNx films were characterized by using atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. The results revealed that the surface roughness increased and both [N]/[C] and sp3/sp2 carbon ratio decreased with increasing bombarding energy. Nanoindentation test indicated that hardness of the CNx films decreased with increasing bombarding energy. Surface free energy of the CNx films was calculated based on the results of contact angle measurement. Values of the surface free energy exhibited slight difference for different CNx films.

► CNx films were synthesized by IBAD with different bombarding energy of N ions.
► N content of the films decreased with increasing bombarding energy.
► The decrease of sp3/sp2 and [N―C]/[N≡C] resulted in film hardness decreasing.
► The surface free energy is composed of high dispersive and low polar components.