Mechanical Deformation Distinguishes Tunneling Pathways in Molecular Junctions

Zuoti Xie, Ioan Bâldea, Greg Haugstad, Daniel Frisbie

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Developing a clearer understanding of electron tunneling through molecules is a central challenge in molecular electronics. Here we demonstrate the use of mechanical stretching to distinguish orbital pathways that facilitate tunneling in molecular junctions. Our experiments employ junctions based on self-assembled monolayers (SAMs) of homologous alkanethiols (CnT) and oligophenylene thiols (OPTn), which serve as prototypical examples of σ-bonded and π-bonded backbones, respectively. Surprisingly, molecular conductances (G molecule ) for stretched CnT SAMs have exactly the same length dependence as unstretched CnT SAMs in which molecular length is tuned by the number of CH 2 repeat units, n. In contrast, OPTn SAMs exhibit a 10-fold-greater decrease in G molecule with molecular length for stretched versus unstretched cases. Experiment and theory show that these divergent results are explained by the dependence of the molecule-electrode electronic coupling δ on strain and the spatial extent of the principal orbital facilitating tunneling. In particular, differences in the strain sensitivity of δ versus the repeat-length (n) sensitivity can be used to distinguish tunneling via delocalized orbitals versus localized orbitals. Angstrom-level tuning of interelectrode separation thus provides a strategy for examining the relationship between orbital localization or delocalization and electronic coupling in molecular junctions and therefore for distinguishing tunneling pathways.

Original languageEnglish (US)
Pages (from-to)497-504
Number of pages8
JournalJournal of the American Chemical Society
Volume141
Issue number1
DOIs
StatePublished - Jan 9 2019

Bibliographical note

Funding Information:
C.D.F. acknowledges financial support from the U.S. National Science Foundation (CHE-1708173). I.B acknowledges financial support from the Deutsche Forschungsgemeinschaft (DFG grant BA 1799/3-1) and partial computational support from the State of Baden-Württemberg and the DFG through grant no. INST 40/467-1 FUGG. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC program.

How much support was provided by MRSEC?

  • Shared

Reporting period for MRSEC

  • Period 5

PubMed: MeSH publication types

  • Journal Article

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