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A surprising way to control the charge transport in molecular electronics: the subtle impact of the coverage of SAM of floppy molecules adsorbed on electrodes

Abstract

. Inspired by earlier attempts in organic electronics aiming at controlling charge injection from metals into organic materials by manipulating the Schottky energy barrier using self assembled monolayers (SAMs), recent experimental and theoretical works in molecular electronics showed that metal-organic interfaces can be controlled via changes in metal work function induced by SAMs. In this paper we indicate a different route to achieve interface-driven control over the charge transfer/transport at molecular scale. It is based on the fact that, in SAMs based on floppy molecules, the molecular conformation can be tuned by varying the coverage of the adsorbate. We demonstrate this effect with the aid of benchmark molecules often used to fabricate nanojunctions consisting of two rings that can easily rotate relative to each other. We show that, by varying the coverage of the SAM, the twisting angle φ of the molecular species considered can be modified by a factor of two. Given the fact that the low bias conductance G scales as cos2φ, for the molecular species considered this results in a change in G over one order of magnitude. Tuning the twisting angle by controlling the SAM coverage may be significant, e.g, for current efforts to fabricating molecular switches. Conversely, the lack of control over the local SAM coverage may be problematic for the reproducibility and interpretation of measurements on repeatedly formed STM (scanning tunneling microscope) single molecule break junctions.

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Publication details

The article was received on 10 Mar 2017, accepted on 19 May 2017 and first published on 19 May 2017


Article type: Paper
DOI: 10.1039/C7FD00101K
Citation: Faraday Discuss., 2017, Accepted Manuscript
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    A surprising way to control the charge transport in molecular electronics: the subtle impact of the coverage of SAM of floppy molecules adsorbed on electrodes

    I. Baldea, Faraday Discuss., 2017, Accepted Manuscript , DOI: 10.1039/C7FD00101K

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