Coherent Electron Transmission across Nanographenes Tethered to Gold Electrodes: Influence of Linker Topology, Ribbon Width, and Length

Abstract

The conductance of several well-defined and experimentally accessible graphene nanoribbons (GNRs) linked to gold electrodes by thiol groups to form single-molecule junctions is investigated within the nonequilibrium Green’s function formalism coupled to density functional theory. We focus on the change in conduction as a function of the width and length of the ribbons as well as the number and position of the linking groups. The calculations illustrate that the position of the linkers is a key parameter controlling the conductance through the GNRs investigated here, as can be anticipated from their Clar sextet representations. The increase in width yields higher conductance only if accompanied by an increasing number of linkers due to the opening of additional pathways. The decay of transmission with GNR length is close to exponential, with rather low attenuation factors (0.06–0.11 Å–1) that depend on the ribbon topology.