Preparation And Properties Of Non-hydrogenated Diomand-like Carbon And Non-hydrogenated Si-doped Diomand-like Carbon Films

The friction coefficient of diamond-like carbon films with moderate Si is insensitive to relative humidity of surounding environment, however, Si was usualy introduced by silane and tetramethylsilane, which would not only weaken the mechanical strenth of films but do harm to the environment. Therefore, non-hydrogenated diamond-like carbon films were prepared by unbalance magnetron sputtering with graphite target, and then non-hydrogenated Si-doped diamond-like carbon films were deposited by graphite and SiC target with optimized process parameters. X-ray photoelectron spectrometer, scanning electron microscope and Raman spectrometer were used to analysis the chemical composition and micro structure of films, and Knoop microhardness tester, nano indenter, scratch tester and ball-on-disc tribometer were employed to characterise the mechanical and tribological properties. The results are as follows:As the deposition pressure increased, the quantity of sp~3 bonding, nano hardness, Young's elastic modulus and friction coefficient of films decreased, but the adhesion increased, while they changed conversely as the bias voltage increased. The sliding velocity have little effect on friction coefficient of films, while the normal load and environmental humidity have greater influence on it. As the normal load increased, the friction coefficient reduced. At high humidity, the friction coefficient was large, while at low humidity it became lower.As the power density of SiC target increased, the quantity of sp~3 bonding also increased, while the nano hardness and Young's elastic modulus firstly increased at maximum values and then decreased. Unfortunately, the addition of Si failed to improve the adhesive strenth between films and substrate. At low relative humidity about 40%, the addition of Si provided a significant reduction in friction coefficient from 0.277 to 0.066, the higher the concentration of Si, the lower the friction coefficient could be, but the specific wear rate remarkably increased with increasing addition of Si. At high relative humidity about 70%, the addition of Si could hardly have influence on the friction coefficient which fluctuated from 0.146 to 0.168. When the power density of SiC target was 0.07W/cm~2(the content of Si was 3.61at.%), relative humidity has little effect on the friction coefficient of films.