Graphene growth on Cu foils by catalytic decomposition of methane forms predominately single layer graphene films due to the low solubility of carbon in Cu. One of the key issues for the use of CVD graphene in device applications is the influence of defects on the transport properties of the graphene. In particular, the presence of grain boundaries within the graphene film will increase the probability for scattering of carriers, resulting in reduced mobilities. Therefore, an important goal is to develop techniques for growing graphene films with crystallites that have lateral dimensions of a few millimeters or larger. There are several factors that influence the size and orientation of the graphene crystallites such as the size and orientation of the grains within the metal foil, temperature gradients during growth, the hydrocarbon source pressure, and the growth temperature. By growing the graphene films using methane source pressures less than 50 millitorr, preanneal times of approximately an hour, growth temperatures of 1035 °C, and a tented Cu substrate geometry within a conventional tube furnace, graphene crystallites larger than a millimeter in size have been achieved.

Measurements of the graphene growth morphology and surface topography of the Cu substrate have been performed using scanning electron microscopy (SEM). The graphene crystallites show a dendrite pattern, and the Cu substrate typically shows a somewhat faceted structure at this growth temperature. Low energy electron diffraction (LEED) measurements show sharp diffraction spots but with multiple zero-order reflections, which results from the faceted structure of the Cu substrate after growth. Electron backscatter diffraction (EBSD) measurements have been performed on the Cu substrates to determine the crystallographic orientation and size of the substrate grains. Before growth, the average grain size is ~10 μm with a random orientation. After growth, the Cu substrate grain size is on the order of centimeters with a typical orientation towards the {100} surface termination. Synchrotron-based angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) measurements have also been performed to probe the electronic band structure of the graphene. A linear dispersion has been measured in the K direction with the Dirac point located near the Fermi level.