Effects of Ti Doping on Structure and Internal Stress of Amorphous Carbon Films on the γ‑Fe Substrate: Molecular Dynamics Simulation

In this paper, C and Ti were used as the deposition atoms in the molecular dynamics model. The effects of Ti doping percentages (2, 8, 14, and 20 atom %) on the structure and internal stress of a-C films were investigated. The results showed that with the increase in the Ti percentage, the density of the intrinsic zone is gradually increased, while the growth rate is slowly decreased. The internal stress is gradually changed from compressive stress to tensile stress. Among them, when the Ti percentage is 14 atom %, the internal stress is closer to 0. The C percentage with sp3 hybridization is decreased, while those with sp2 and sp hybridizations are increased. The positions of the first and second peaks in the RDF were shifted to the left. Moreover, the distribution of bond lengths and bond angles in the intrinsic zone tend to change from diamond to graphite, which proves that Ti doping leads to the graphitization of a-C films. In addition, Ti doping affects the internal stress of a-C films by changing the C percentage with sp3 hybridization in them.