Structure and properties of carbon nitride films synthesized by low energy ion bombardment

Carbon nitride films have been synthesized at low substrate temperature by Ar+ sputtering a graphite target with concurrent N+ assisted bombardment. It was disclosed that N+ bombardment with low energies of 150-400 eV and beam densities of 0.16-0.23 mA cm(-2) was favorable to grow carbon nitride films with high N/C atomic composition ratios of 0.47-0.56. The spectra of x-ray photoelectron spectroscopy and infrared spectroscopy show that the low energy N+ bombardment activates nitrogen atoms to combine carbon atoms in unpolarized covalent bonds. Under the 150-300 eV and 0.16-0.23 mA cm(-2) N+ assisted bombardment, the formed films are identified by transmission electron microscopy to possess the beta-C3N4 microcrystalline structure. The films exhibit an extremely high hardness of 5260 kgf/mm(2), a high resistivity of 4.8 X 10(12) Ohm X cm, and excellent optical transmittance. Friction and wear tests show that carbon nitride films on steel substrate can perform the even wear in low friction coefficients of 0.05-0.16 while raising wear loads up to 20 N.