Investigating Molecular Junctions Based on Mixed Self-Assembled Monolayers to Understand the Impact of Intermolecular Interactions on Transport.

To interrogate the importance of intermolecular interactions on charge transport at the nanoscale, we investigate molecular tunnel junctions based on mixed self-assembled monolayers (SAMs) of 1-alkyl (CnT) thiols and their fluorinated counterparts (F-CnT) that have substantially different tunneling conductances. Experiments on mixed CnT:F-CnT SAMs between Au contacts reveal a strongly nonlinear (exponential) dependence of the tunneling conductance on composition , a behavior that is tempting to assign to the strong impact of intra-SAM intermolecular interactions. However, analysis suggests that the exponential dependence of on does not arise from intra-SAM intermolecular interactions, but instead emerges from the work function modification of the Au electrode which varies linearly with .