The Carbon's solubility into copper is incredibly small and therefore largely floor diffusion and nucleation of carbon atoms are associated. For that reason as well as growth kinetics, the graphene thickness is restricted to predominantly a monolayer. The big benefit is that the graphene could be grown on Cu foil https://www.quora.com/profile/Trevor-Flatcher-2/Prospects-for-Silicon-Carbide-in-Solar-Cells-Silicon-Carbide-SiC-has-emerged-as-a-promising-material-for-enhancing-th