▎ 摘　　要

We report the reversible oxidation and reduction of single layer graphene on a self-aligned Cu-rich CuOx layer, which was created on a Cu substrate by thermal reduction of a native Cu-oxide layer while forming graphene on top of the Cu by chemical vapor deposition. The reversible oxidation states of graphene, revealed by X-ray photoemission and Raman spectroscopies, were driven by migration of oxygen ions in the CuOx layer under external electrostatic bias. Breaking the translational symmetry of the C-C sp(2) bonds by the migrated oxygen resulted in a noticeable D band peak in the Raman spectra. However, the D band peak was not completely reduced under reverse external bias, indicating a certain level of permanent oxygen bonding on the graphene. First-principles density functional theory calculations suggested two distinct graphene-oxygen bonding configurations i.e., (1) a most-stable epoxy-like bridged oxygen and (2) a meta-stable ketone-like on-top oxygen in a four-membered ring configuration, which might be responsible for the irreversible and reversible oxidation states of graphene, respectively. (C) 2013 Elsevier B.V. All rights reserved.