Microstructure and property evolution of diamond-like carbon films co-doped by Al and Ti with different ratios

Abstract

Diamond-like carbon (DLC) films with weak carbide metal Al and carbide metal Ti co-doping (Al/Ti-DLC) were prepared by a hybrid ion beam deposition system. The atomic ratios of doped Al to Ti were tailored via designing the special Al/Ti combined sputtering target. The composition, microstructure, roughness, residual stress, hardness, toughness, and tribological behaviors of the deposited films were systematically evaluated to explore the dependence of structural properties on Al/Ti ratios. Results indicated that the high-throughput preparation of DLC films with different Al/Ti atomic ratios was achieved by tailoring the sputtering target and process parameters without the difference in both the film thickness and total Al/Ti content. With the Al/Ti ratios in the films decreased from 8.8 to 3.0, the residual stress, hardness, and toughness of Al/Ti-DLC films increased obviously, originating from the increased fraction of titanium carbide and the reduced Al content. However, the coefficient of friction and wear rate with decreasing the Al/Ti ratio were obviously improved, which was related with the transformation of underlying friction mechanism from the sliding interface graphitization to dangling bond-passivation. The present results not only suggest a high-throughput method to fabricate co-doped DLC films, but also promote the scientific understanding and engineering application of DLC films with high performance.