CARBON, vol.109, pp.529-541, 2016 (SCI-Expanded)
Low-pressure chemical vapor deposition synthesis of graphene films on two different Cu foils, with different surface oxygen and carbon contents, was performed by controlling H-2 and/or Ar flow rates during heating. The influences of heating atmosphere on the final impurity level, quality of the synthesized graphene films and thickness uniformity were investigated depending on Cu foil impurities. Heating of carbon-rich, but oxygen-poor Cu foil in H-2 environment resulted in covering the foil surface by residual carbon which then acted as active sites for multilayer graphene growth. Ar-only flow was required during heating to promote high quality graphene growth on this foil. On carbon-poor, but oxygen-rich Cu foil high quality graphene growth was promoted when the heating was carried out under Ar/H-2 environment. Almost no carbon residues were observed on this foil even under H-2 only flow during heating. The heating atmosphere affected not only graphene growth, but also the type and amount of impurities formed on the surface. H-2 and Ar/H-2 heating resulted in the formation of spherical nanometer-sized impurities, while irregular-shaped, large (a few mu m) SiO2 impurities were observed when Ar alone was used during heating. Quality of the grown films was tested by Quantum Hall Effect measurements. (C) 2016 Elsevier Ltd. All rights reserved.