Comparative study on structure and properties of titanium/silicon mono- and co-doped amorphous carbon films deposited by mid-frequency magnetron sputtering

The titanium/silicon mono- and co-doped amorphous carbon films were deposited by mid-frequency magnetron sputtering Ti target, Si target, and Ti80S20 alloy target, respectively. The effects of doped elements on the composition, surface morphology, microstructure, and mechanical and tribological properties of the films were investigated. The results reveal that the ratio of sp³ and sp² carbon bonds of the films is regulated between 0.28 and 0.62 by a combination of Ti and Si dopant. The addition of small amounts of silicon leads to an increase in sp³ bonds and disorder degree of the sp² carbon. The co-doped film exhibits significantly superior friction performance than the mono-doped films. The ultra-low friction (μ < 0.01) was achieved under a load of 2 N in ambient air with 40% RH. By comparing to the mono-and co-doped films, it is thought that the sp³/sp² ratio of the films may play a key role for the superlow friction.