The carbon's solubility into copper is incredibly minimal and so mostly floor diffusion and nucleation of carbon atoms are concerned. Because of this and also the growth kinetics, the graphene thickness is restricted to predominantly a monolayer. The massive edge is that the graphene could be grown on Cu foil https://www.quora.com/profile/Trevor-Flatcher-2/Innovative-Applications-of-Silicon-Carbide-in-Medical-Devices-Silicon-carbide-SiC-has-emerged-as-a-revolutionary-mate