The Carbon's solubility into copper is incredibly low and therefore primarily surface diffusion and nucleation of carbon atoms are involved. Because of this and also the growth kinetics, the graphene thickness is restricted to predominantly a monolayer. The large edge is that the graphene could be developed on Cu foil https://www.quora.com/profile/Trevor-Flatcher-2/Role-of-Silicon-Carbide-in-Fuel-Cells-Silicon-carbide-SiC-plays-a-crucial-role-in-advancing-fuel-cell-technology-off