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

Feng, Jiajun; Bâldea, Ioan; Gao, Jiajie; Jeong, Gookyeong; Frisbie, C Daniel; Xie, Zuoti · ACS Nano · 2024

basic_science · Level V

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Abstract

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<sub>1-<i>x</i></sub>:F-CnT<sub><i>x</i></sub> SAMs between Au contacts reveal a strongly nonlinear (exponential) dependence of the tunneling conductance <i>G</i> on composition <i>x</i>, a behavior that is tempting to assign to the strong impact of intra-SAM intermolecular interactions. However, analysis suggests that the exponential dependence of <i>G</i> on <i>x</i> does not arise from intra-SAM intermolecular interactions, but instead emerges from the work function modification of the Au electrode which varies linearly with <i>x</i>.