Effective Reduction of Copper Surface for Clean Graphene Growth

We developed a new pre-reduction method of Cu surface (using (NH4)(2)S2O8 etching solution) for high quality graphene growth. The adsorbed oxygen and water molecules on the bare Cu surface produce CuO2 and Cu(OH)2 bonding, resulting in physical degradation of continuous monolayer graphene by forming CuOx nano-particles at the interface between graphene and Cu catalyst. The chemical degradation of graphene was also confirmed by analyzing the sp(3)/sp(2) C-C bond ratio using X-ray photoemission. The conventional reduction method such as hydrogen reduction and acetic acid pre-treatment was not sufficient to remove these CuOx nano-particles. We demonstrated that the pre-etched Cu foil in 0.3 mole (NH4)(2)S2O8 solution for 1 mm can be the most ideal candidate for the high quality and clean graphene growth. (C) 2015 The Electrochemical Society. All rights reserved.