Issue 1, 2016

Transition voltages respond to synthetic reorientation of embedded dipoles in self-assembled monolayers

Abstract

We studied the influence of embedded dipole moments in self-assembled monolayers (SAMs) formed on template stripped Au surfaces with liquid eutectic Ga–In alloy as a top electrode. We designed three molecules based on a p-terphenyl structure in which the central aromatic ring is either phenyl or a dipole-inducing pyrimidyl in one of two different orientations. All three form well defined SAMs with similar thickness, packing density and tilt angle, with dipole moments embedded in the SAM, isolated from either interface. The magnitude of the current density is dominated by the tunneling distance and is not affected by the presence of dipole moments; however, transition voltages (VT) show a clear linear correlation with the shift in the work function of Au induced by the collective action of the embedded dipoles. This observation demonstrates that VT can be manipulated synthetically, without altering either the interfaces or electrodes and that trends in VT can be related to experimental observables on the SAMs before installing the top contact. Calculated projected density of states of the SAMs on Au surfaces that relate HOMO-derived states to VT further show that energy level alignment within an assembled junction can be predicted and adjusted by embedding dipoles in a SAM without altering any other properties of the junction. We therefore suggest that trends in VT can be used analogously to β in systems for which length-dependence is physically or experimentally inaccessible.

Graphical abstract: Transition voltages respond to synthetic reorientation of embedded dipoles in self-assembled monolayers

Supplementary files

Article information

Article type
Edge Article
Submitted
20 Aug 2015
Accepted
17 Oct 2015
First published
22 Oct 2015
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2016,7, 781-787

Author version available

Transition voltages respond to synthetic reorientation of embedded dipoles in self-assembled monolayers

A. Kovalchuk, T. Abu-Husein, D. Fracasso, D. A. Egger, E. Zojer, M. Zharnikov, A. Terfort and R. C. Chiechi, Chem. Sci., 2016, 7, 781 DOI: 10.1039/C5SC03097H

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