Two selective growth modes for graphene on a Cu substrate using thermal chemical vapor deposition

Here we provide evidence of two selective growth modes, namely the 'surface adsorption (SA) mode' and the 'diffusion and precipitation (DP) mode' for the synthesis of graphene on Cu foil by thermal chemical vapor deposition. Using acetylene feedstock, the number of graphene layers was controlled simply by adjusting the injection time, and the DP growth mode was clearly verified by the existence of a carbon-diffused Cu layer with expansion of the Cu lattice. With methane feedstock, either SA or DP growth modes could be selected for the growth of graphene at low or high partial pressure of carbon feedstocks, respectively. The critical pressure for switching the growth modes depends on reactivity of carbon feedstock to Cu substrate.