Surface roughness, scratch resistance and tribological properties of hydrogenated amorphous carbon coatings prepared by low-pressure dielectric barrier discharge

In this study, we explored the surface roughness, scratch resistance and tribological properties of hydrogenated amorphous carbon (a-C:H) coatings deposited on silicon substrates from low-pressure dielectric barrier discharge (DBD) plasmas of CH4 by using an atomic force microscope (AFM), AFM-based scratch testing technique and lateral force microscope. The AFM and scratch measurements show that the surface roughness and scratch resistance of these a-C:H coatings strongly depend on the Pd value (the product of CH4 pressure P, and discharge gas spacing d) and the a-C:H coatings deposited at suitable Pd value (typically 350 Pa mm) exhibit lower surface roughness and better scratch resistance. The a-C:H coatings deposited at the Pd value of 350-1750 Pa mm have the typical friction coefficient of approximately 0.13. The lower friction coefficient (0.11) of the a-C:H coating deposited at the smaller Pd value of 245 Pa mm can be associated with its graphite-like surface structure. The results indicate the coating structure changes from the one of graphite-like to diamond-like to polymer-like with the Pd value increasing from 245 to 1750 Pa mm. The relationship between the measured coating properties and the DBD deposition processes was presented. (C) 2003 Elsevier Science B.V All rights reserved.