Initial Stage of Graphene Growth on a Cu Substrate

The growth of graphene on copper foil has attracted attention in the last two years due to its feasibility for a controllable growth process. One of the key issues remaining for practical application of graphene in solid-state devices is growth with a large grain size. Because the C-C bond in graphene is strong enough to prevent the evaporation-condensation process, Smoluchowski ripening is expected to be the dominant process for coalescence. In this article, we present the initial growth process of graphene on a Cu foil via the chemical vapor deposition method by using secondary electron microscopy and Raman microscopy. In contrast to the other transition-metal substrates, such as Ir and Rh, the center of graphene islands binds to the substrate more rigidly than the edge. For the growth with a large grain size, the graphene should be grown on a substrate with a low diffusion barrier for the carbon clusters (or islands) with low flux; this is the controlling parameter for the grain size. In addition, high-temperature growth (or annealing) generally becomes a dominant condition for the completion of graphene growth with large grains after the coalescence.