Growth of Large-Area Single- and Bi-Layer Graphene by Controlled Carbon Precipitation on Polycrystalline Ni Surfaces

We report graphene films composed mostly of one or two layers of graphene grown by controlled carbon precipitation on the surface of polycrystalline Ni thin films during atmospheric chemical vapor deposition(CVD).Controlling both the methane concentration during CVD and the substrate cooling rate during graphene growth can signifi cantly improve the thickness uniformity.As a result,one-or two-layer graphene regions occupy up to 87%of the fi lm area.Single layer coverage accounts for 5%11%of the overall fi lm.These regions expand across multiple grain boundaries of the underlying polycrystalline Ni fi lm.The number density of sites with multilayer graphene/graphite(>2 layers)is reduced as the cooling rate decreases.These fi lms can also be transferred to other substrates and their sizes are only limited by the sizes of the Ni fi lm and the CVD chamber.Here,we demonstrate the formation of fi lms as large as 1 in^(2).These fi ndings represent an important step towards the fabrication of large-scale high-quality graphene samples.