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Charge Transfer Complexation Boosts Molecular Conductance Through Fermi Level Pinning

preprint
submitted on 20.09.2018 and posted on 21.09.2018 by Kun Wang, Andrea Vezzoli, Iain Grace, Maeve McLaughlin, Richard Nichols, Bingqian Xu, Colin Lambert, Simon Higgins
We have used scanning tunneling microscopy to create and study single molecule junctions with thioether-terminated oligothiophene molecules. We find that the conductance of these junctions increases upon formation of charge transfer complexes of the molecules with tetracyanoethene, and that the extent of the conductance increase is greater the longer is the oligothiophene, i.e. the lower is the conductance of the uncomplexed molecule in the junction. We use non-equilibrium Green's function transport calculations to explore the reasons for this theoretically, and find that new resonances appear in the transmission function, pinned close to the Fermi energy of the contacts, as a consequence of the charge transfer interaction. This is an example of a room temperature quantum interference effect, which in this case boosts junction conductance in contrast to earlier observations of QI that result in diminished conductance.

Funding

UK EPSRC, grants EP/H035818/1, EP/H035184/1, EP/M005046/1; US NSF grants ECCS 1609788, ECCS 1231967.

History

Email Address of Submitting Author

shiggins@liverpool.ac.uk

Institution

University of Liverpool

Country

United Kingdom

ORCID For Submitting Author

0000-0003-3518-9061

Declaration of Conflict of Interest

None

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