Ab initio molecular dynamics simulation on stress reduction mechanism of Ti-doped diamond-like carbon films

Structural properties of Ti-doped diamond-like carbon (DLC) films as a function of Ti concentrations (1.56-7.81 at.%) were investigated by ab initio molecular dynamics simulation to clarify the stress reduction mechanism. Results showed that with introducing Ti into DLC films, the residual compressive stress decreased firstly and then increased, which was consistent with the previous experimental results. Structural analysis revealed that the addition of Ti efficiently relaxed both the highly distorted bond angles and bond lengths, which led to the reduction of residual stress; the increase of residual stress at the high Ti concentration was attributed to the existence of distorted Ti-C structures and the increased fraction of distorted CC bond lengths.