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

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Abstract
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 β–C3N4 microcrystalline structure. The films exhibit an extremely high hardness of 5260 kgf/mm2, a high resistivity of 4.8 × 1012 Ω × 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.