The Carbon's solubility into copper is extremely reduced and so generally floor diffusion and nucleation of carbon atoms are associated. For that reason and also the growth kinetics, the graphene thickness is limited to predominantly a monolayer. The big benefit is that the graphene might be developed on Cu foil https://www.quora.com/profile/Trevor-Flatcher-2/Thermal-Conductivity-of-Silicon-Carbide-and-Heat-Dissipation-Solutions-for-Electronic-Devices-Thermal-management-is-a-c