The role of trace Ti concentration on the evolution of microstructure and properties of duplex doped Ti(Ag)/DLC films

Trace Ag-Ti co-doped diamond-like carbon (DLC) films were prepared on stainless steel and silicon (100) substrates by medium frequency unbalanced magnetron sputtering with Ar and CH4 as source gases. The effects of sputtering current of Ti target on the microstructure, mechanical and tribological properties were investigated with the content and format of the doped Ag keeping constant. It can be seen the Ti concentration and sp2C content in the film increase with increasing Ti sputtering current. Furthermore, the doped Ti species changed from the form of metallic phase to TiC with increasing Ti concentration, and the hardness and internal stress of the film decrease firstly and then increase, which is related with the microstructural change induced by trace Ti incorporation. Finally, the duplexed-nanocomposite film with 1.600 at.% Ti shows relatively high hardness and H/E and H3/E2 ratio, which is mainly responsible for the superior tribological properties.