Nickel-Mediated in Situ Growth Mechanism of Top-Layered Graphene in the Vicinity of Diamond Grain Boundary: A Theoretical Study

The growth of graphene on insulating materials is always a focused issue in the field of multifunctional nanomaterials. To investigate the atomistic mechanism of graphene growth on bi-crystal diamonds, we initially investigated the process of in situ growth of graphene on bi-crystal diamonds in the presence of a nickel catalyst and further explored the diamond grain boundary (GB) effect on the graphene growth by reactive molecular dynamics (MD) simulations. The detailed dynamic evolution of graphene growth, the counterdiffusion of catalytic nickel atoms/GB carbon atoms, and the consequent amorphization of GB were observed. The study demonstrated that the presence of GB assists graphene growth, namely, the amorphous C_GBatoms participate in the growth of graphene as supplementary carbon atoms, which is in good qualitative agreement with experimental observations. In addition, we demonstrated that the amorphization of GB is caused by the increase of energy at GB driven by the catalysis of nickel atoms. The results further indicate that the diffusion behavior of the amorphous C_GBatom in the nickel lattice involves irregular lateral migration instead of pure upward diffusion. In contrast, in the absence of GB, the kinetics of nickel catalyst-induced amorphization of diamond structures is drastically impaired, resulting in lower graphene coverage.