Transport properties of zigzag graphene nanoribbons with oxygen edge decoration

Using the density functional theory in combination with the nonequilibrium Green's function method, we investigate the transport properties of zigzag-edged graphene nanoribbons (ZGNRs) with oxygen edge decoration (passivated by the ketone (C=O) or ether (C-O-C), denoting as ZGNR-CO and ZGNR-C2O, respectively). We find that both ZGNR-CO and ZGNR-C2O induce the semiconductor-metal transition and enhance the transmission conductance within 'transparent' electrodes. However, sandwiched by Au (111) electrodes, Au vertical bar ZGNR - CO vertical bar Au enhances the transport properties while Au vertical bar GNR - C2O vertical bar Au depresses the transport properties in comparison with Au vertical bar ZGNR - H vertical bar Au. It is found that the transport properties of the edge oxidized ZGNRs within Au (111) electrodes depend on the electronic states around the Fermi level which determine the number of the effective transport channels. The states of Au vertical bar ZGNR - CO vertical bar Au are delocalized on the edge oxygen atoms as well as the inner edge carbon atoms, introducing extra transport channels. Moreover, in comparison with Au vertical bar ZCNR - H vertical bar Au, the effective transport channels of Au vertical bar ZGNR - CO vertical bar Au increase at given applied bias. However, the states of Au vertical bar ZGNR - C2O vertical bar Au, are localized on the ribbon, blocking the effective transport channels. (C) 2012 Elsevier B.V. All rights reserved.