Unveiling the site-dependent characteristics and atomic mechanism of graphene growth on the polycrystalline diamond: Insight from the experiments and ReaxFF studies

The synthesis of graphene on functional materials has been an issue of great interest in the field of new-functional nanomaterials. As a promising semiconductor and mechanical material, the need for direct growing graphene on the polycrystalline diamond for modification has been strongly inspired nowadays. Herein, we completed the catalytic thermal annealing synthesis of graphene on the polycrystalline diamond without any additional carbon source, and the site-dependent growth characteristics of graphene on the diamond materials were captured. To explain such growth characteristics in detail, the graphene in-situ growth mechanism based on the polycrystalline diamond surface was clarified for the first time by using the reactive molecular dynamics method. Essentially, the growth mechanism of graphene in the vicinity of the diamond grain boundary follows the principle of "counter-precipitation". Furthermore, the graphene growth is driven by the amorphization of the diamond lattice, and the pristine diamond surface has been proven can be used as the only solid carbon source to accomplish the growth of graphene on it. By contrast, the grain boundary plays the role of supplementary solid carbon source to accelerate the graphene growth rate during the graphene growth, which is the underlying cause of the site-dependent growth characteristics of graphene on the polycrystalline diamond.