Using ab initio transport methods, we investigate electron transmission modes (channels, pathways, and intensities) in electrically biased graphene nanoribbons (GNRs) under different growth conditions. In addition to the bond currents, we report loop currents in such devices, induced by the electrons hopping between carbon atoms of the same sublattice under bias. The loop current channel as well as the bond current channel play an important role in the local current in electrically biased GNR-based devices. The effect of edge functional groups and surface defects/groups on device performance depends on the current pathway and intensity in these two channels. Understanding the details of local currents in GNRs paves the way to make high-performance GNR-based electronic devices, such as GNR field effect transistors.

• Received 4 November 2011

DOI:https://doi.org/10.1103/PhysRevB.86.115419