The impact of collective electrostatic effects on molecular electronics
Veronika Obersteiner [1], David A. Egger [1],[2], Georg Heimel [3], Egbert Zojer [1]
[1] Institute of Solid State Physics, Graz University of Technology; [2] Department of Materials and Interfaces, Weizmann Institute of Science; [3] Institut für
http://www.if.tugraz.at/
10:00 - 10:20 Thursday 23 October 2014 Rechbauerstrasse 12, HSII Molecular electronics is a branch of nanotechnology where few or even individual molecules are considered as basic building blocks for applications on the nanoscale. Based on the bottom-up approach it offers the opportunity to sandwich single molecules between electrodes, with the vision of supporting and extending conventional semiconductor technologies in the future.
For advancing this exciting field, a microscopic understanding of charge transport through molecule-based systems is essential. Over the past years, the fundamental physical differences between devices comprising an individual molecule or a homogeneous monolayer have been increasingly acknowledged. Here, we relate those differences to collective electrostatic interactions among the molecules. Employing density functional theory in conjunction with a Green's function approach, we theoretically investigate current-voltage (IV-) characteristics of metal-molecule-metal systems that comprise either single molecules or an assembly of them.
We show that, depending on the chemical nature of the involved molecules, collective effects due to neighboring molecules either significantly increase or decrease the current flowing at a given bias. These insights are used to chemically design molecules in which collective effects cancel, and thus the molecular electrical characteristics remain unaffected by environmental effects. This could be exploited for reducing fluctuations arising from structural imperfections in monolayer devices caused by lateral variations of the local packing density.
In experimental characterizations of molecular devices one often probes finite assemblies of molecules rather than only a single entity. We therefore additionally study the role of collective effects for molecular clusters of varying size. These results help understanding for how many molecules collective electrostatic effects start to appear.
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