Effect of deposition pressure on the adhesion and tribological properties of a-CN _x H films prepared by DC-RF-PECVD

Hydrogenated carbon nitride (a-CN _x H films) was deposited on n-type single-crystal Si (100) by direct current radio frequency plasma-enhanced chemical vapor deposition (DC-RF-PECVD), under the working pressure of 5.0-17.0 Pa, using the CH₄ and N₂ as feedstock. The composition and surface morphology of the a-CN _x H films were characterized by means of Raman spectroscopy and atomic force microscopy, while the Young's modulus, elastic recovery, adhesion strength, and tribological properties were evaluated using nano-indentation, scratch test and friction test system. It was found that the surface roughness and Raman spectra peak intensity ratio I _D/I _G of the films increased with the increase of working pressure, while the Young's modulus, elastic recovery and adhesion strength of the films significantly decreased. Moreover, the tribological properties of the films also varied with the working pressure. The wear life sharply increased with the increase of working pressure from 5.0 Pa to 7.5 Pa, further, an increase in the deposition pressure led to a gradual decrease in the wear life, consequently, the a-CN _x H film deposited at 7.5 Pa exhibited the longest wear life. The deposition pressure seemed to have slight effect on the average friction coefficients, whereas the surface roughness and adhesion strength have deteriorated with increasing deposition pressure.