Studies on the influence of sputtering power on amorphous carbon films deposited by pulsed unbalanced magnetron sputtering

Amorphous carbon (a-C) films were deposited by pulsed unbalanced magnetron sputtering technique under different sputtering powers from 100 to 220 W. The film thickness, bonding configuration, mechanical and optical properties of these films were investigated by various techniques. It is found that the film thickness of a-C films increases with the increase of sputtering power. The results of X-ray photoelectron spectroscopy analysis suggest that the sp3/sp2 ratio in the films increases with increasing sputtering power from 100 to 180 W, and then decreases with increasing sputtering power from 180 to 220 W. Mechanical and optical properties measurements show that the nanohardness, refractive index and optical band gap increase with increasing sputtering power from 100 to 180 W, and then decreases with the further increase of sputtering power; the extinct coefficient decreases first and then increases with increasing sputtering power. The results above indicate that sputtering power has a significant influence on the microsturture and properties of a-C films deposited by pulsed unbalanced magnetron sputtering technique.