Study on the microstructure and properties of graphite-like carbon films deposited by unbalanced magnetron sputtering

Abstract

A series of graphite-like amorphous carbon films were deposited by unbalanced magnetron sputtering system with different sputtering currents. The microstructure, morphology, contact angle, and tribological properties of the resultant carbon films were subsequently investigated by means of different characterization techniques. Raman analysis shows that the resultant amorphous carbon films are dominated by sp2 sites, and the intensity ratio of the D and G peaks increases gradually from ∼4.1 to ∼5.4 with decrease in the sputtering current from 16 to 4 A, which is one order of magnitude larger than that of diamond-like carbon films with high sp3 content, indicating a more graphite-like structure. The surface of the resulting carbon films is composed of granular structure with different diameters and heights, and the root mean square roughness of the studied films monotonically increases from 3.5 nm at a sputtering current of 4 A to 8.2 nm at 16 A. The contact angle of graphite-like carbon films with water changes from 43.4° to 89.5° with decrease in the sputtering current. Besides, these graphite-like carbon films demonstrate superior tribological properties with high load-bearing capacity and low friction coefficient in humid atmosphere. The superior tribological behaviors of this graphite-like carbon film are promising for a wide range of applications such as gears, cutting tools, automobile parts, etc.