Effect of Substrate Roughness and Feedstock Concentration on Growth of Wafer-Scale Graphene at Atmospheric Pressure

The growth of large-area graphene on catalytic metal substrates is a topic of both fundamental and technological interest. We have developed an atmospheric pressure chemical vapor deposition (CVD) method that is potentially more cost-effective and compatible with industrial production than approaches based on synthesis under high vacuum. Surface morphology of the catalytic Cu substrate and the concentration of carbon feedstock gas were found to be crucial factors in determining the homogeneity and electronic transport properties of the final graphene film. The use of an electropolished metal surface and low methane concentration enabled the growth of graphene samples with single layer content exceeding 95%. Field effect transistors fabricated from CVD graphene made with the optimized process had room temperature hole mobilities that are a factor of 2-5 larger than those measured for samples grown on as-purchased Cu foil with larger methane concentration. A kinetic model is proposed to explain the observed dependence of graphene growth on catalyst surface roughness and carbon source concentration.