Amorphous carbon to graphene: Carbon diffusion via nickel catalyst.

• The diffusion process of carbon in graphene formation via nickel catalyst was studied from experiments and simulations. • The diffusion barrier of carbon in nickel was calculated based on first principles. • Carbon diffused along nickel grain boundaries preferentially because of the lower diffusion barrier. • Graphene was formed on nickel surface due to metal-induced and diffusion-assisted mechanism. Graphene can be synthesized via metal catalysis using solid carbon source. In this paper, graphene was fabricated using amorphous carbon. We further elucidated the process of carbon diffusion and graphene formation at low temperatures using a comprehensive experimental and theoretical strategy. The diffusion barrier of carbon in nickel crystal is different from that of carbon along nickel grain boundaries, resulting in that the layer of graphene is uncontrollable. Based on our findings, we identified the causes of graphene heterogeneity and the process of carbon diffusion. [ABSTRACT FROM AUTHOR]