Modulation of the band gap of graphene oxide: The role of AA-stacking

The unique electronic properties of graphene make it an advantageous material for use in many applications, except those that require a band gap. Much work has been done to introduce an appropriately tuned band gap into graphene, including uniaxial strain and oxidation, with varying levels of success. We report here that the stacking configuration of the sheets in multilayered graphene oxide can have a significant impact on the band gap. Through comparison of X-ray absorption near-edge spectra of multilayered pristine graphene sheets with spectra simulated using density functional theory, we have found that AA-stacking pushes unoccupied states closer to the Fermi level than AB-stacking by widening the pi* resonance in both graphene oxide and graphene. If the near-Fermi states have been removed such that the nearest unoccupied state to the Fermi level is the pi* band, then AA-stacked multilayered graphene oxide will have a smaller band gap than AB-stacked graphene oxide. We have confirmed this by measuring the band gap of graphene oxide and reduced graphene oxide indirectly using X-ray absorption near-edge spectroscopy and X-ray emission spectroscopy. Controlling the stacking configuration of multilayered graphene oxide may provide a novel method for tuning its band gap. (C) 2013 Elsevier Ltd. All rights reserved.