Quantifying Molecular Structure-Tunneling Conductance Relationships: Oligophenylene Dimethanethiol vs Oligophenylene Dithiol Molecular Junctions

Quyen Van Nguyen, Zuoti Xie, C. Daniel Frisbie

Research output: Contribution to journalArticlepeer-review

Abstract

We report quantitative analysis of tunneling conductance in molecular junctions based on self-Assembled monolayers (SAMs) of oligophenylene dimethanethiols (OPDMn) in which-CH2-spacers flank either side of the phenylene (n = 1), biphenylene (n = 2), and terphenylene (n = 3) aromatic cores. The current-voltage (I-V) characteristics for the OPDMn junctions with Au and Pt contacts are analyzed quantitatively with a previously validated single level model (SLM) to extract key junction metrics, namely the HOMO-To-Fermi-level offset, h, and the electronic coupling, . Independent determination of h by ultraviolet photoelectron spectroscopy (UPS) corroborates the estimation of h from the I-V characteristics and provides strong evidence for the validity of the SLM analysis. Further, comparison of the results for OPDMn junctions with those for oligophenylene dithiol (OPDn) junctions, which do not have-CH2-spacers, reveals that the much larger resistance for OPDMn (1000-fold) is primarily due to a 50-fold decrease in and not to any significant change in h; h is nearly identical for OPDMn and OPDn junctions for each value of n. Overall, our results provide a clear delineation of the influence of-CH2-spacers on h and and give further evidence that the analytical SLM is a useful tool for determining structure-Transport relationships in molecular tunnel junctions.

Original languageEnglish (US)
Pages (from-to)4292-4298
Number of pages7
JournalJournal of Physical Chemistry C
Volume125
Issue number7
DOIs
StatePublished - Feb 10 2021

Bibliographical note

Funding Information:
The authors acknowledge the financial support of the National Science Foundation (CHE-2003199). Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (Award Number DMR-2011401) and NNCI programs (Award Number ECCS-2025124).

Publisher Copyright:
© 2021 American Chemical Society. All rights reserved.

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