Graphene as a Promising Electrode for Low-Current Attenuation in Nonsymmetric Molecular Junctions

Abstract

High Resolution Image Download MS PowerPoint Slide We have measured the single-molecule conductance of 1, n -alkanedithiol molecular bridges ( n = 4, 6, 8, 10, 12) on a graphene substrate using scanning tunneling microscopy (STM)-formed electrical junctions. The conductance values of this homologous series ranged from 2.3 nS ( n = 12) to 53 nS ( n = 4), with a decay constant β n of 0.40 per methylene (−CH 2 ) group. This result is explained by a combination of density functional theory (DFT) and Keldysh–Green function calculations. The obtained decay, which is much lower than the one obtained for symmetric gold junctions, is related to the weak coupling at the molecule–graphene interface and the electronic structure of graphene. As a consequence, we show that using graphene nonsymmetric junctions and appropriate anchoring groups may lead to a much-lower decay constant and more-conductive molecular junctions at longer lengths.