Influence of flow ratio on mechanical and tribological properties of hydrogenated carbon nitride films prepared by DC-RF-PECVD

Amorphous hydrogenated carbon nitride (a-CN : H) films were deposited onto silicon (n-100) substrates by dual direct current radio frequency plasma enhanced chemical vapour deposition with CH₄ and N₂ as feedstock at different ratios. The composition and surface morphology of the films were characterized by means of x-ray photoelectron spectroscopy, Raman spectroscopy and atomic force microscopy; while the mechanical and tribological properties of the films were evaluated using nano-indentation and the UMT test system. It was found that the deposition rate of the films decreased significantly but the N/C ratio, the surface roughness and the I _D/I_G ratio of the films increased as the N ₂/CH₄ flow ratio increased. The nano-hardness and adhesion strength of the films to the silicon substrate sharply increased at first and then decreased with increasing N₂/CH₄ flow ratio. Moreover, the wear resistance of the films varied with the N₂/CH ₄ flow ratio. The structure transformation from an sp ³-like to sp²-like carbon-nitrogen network in the deposited films was also revealed.