Significant enhancement of the electrical transport properties of graphene films by controlling the surface roughness of Cu foils before and during chemical vapor deposition

We have studied the influence of the surface roughness of copper foils on the sheet resistance of graphene sheets grown by chemical vapor deposition. The surface roughness of the copper foils was reproducibly controlled by electropolishing. We have found that the graphene sheet resistance monotonically decreases as the surface roughness of the copper foils decreases. We show that a pre-annealing treatment combined with an optimized electropolishing process of the Cu foils and a fast CVD growth prevents the evolution of the Cu surface roughness during graphene synthesis. This combination of fabrication conditions produces small grain polycrystalline graphene films with a sheet resistance of 210 Ω □^-1 and carrier mobility values as high as 5450 cm² V^-1 s^-1 after transfer onto SiO₂/Si.