Revealing the Role of Anchoring Groups in the Electrical Conduction Through Single-Molecule Junctions

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 6; no. 14; pp. 1529 - 1535
• Main Authors: Zotti, Linda A., Kirchner, Thomas, Cuevas, Juan-Carlos, Pauly, Fabian, Huhn, Thomas, Scheer, Elke, Erbe, Artur
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 19.07.2010; WILEY‐VCH Verlag
• Subjects: Anchoring; anchoring groups; break junctions; Coupling (molecular); density functional theory; Electric Conductivity; Electrical junctions; Electrodes; Fermi surfaces; Mathematical models; Models, Theoretical; molecular electronics; molecular wires; Strength; Transport
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.200902227

A combined experimental and theoretical study is presented revealing the influence of metal–molecule coupling on electronic transport through single‐molecule junctions. Transport experiments through tolane molecules attached to gold electrodes via thiol, nitro, and cyano anchoring groups are performed. By fitting the experimental current–voltage characteristics to a single‐level tunneling model, we extract both the position of the molecular orbital closest to the Fermi energy and the strength of the metal–molecule coupling. The values found for these parameters are rationalized with the help of density‐functional‐theory‐based transport calculations. In particular, these calculations show that the anchoring groups determine the junction conductance by controlling not only the strength of the coupling to the metal but also the position of the relevant molecular energy levels. Attaching molecules to metallic electrodes in order to establish a reliable electrical contact is still an open task in the field of molecular electronics. By inspection of the current–voltage characteristics and comparison to theoretical model descriptions, insight is gained into the role of the anchoring groups in the electrical properties of the molecules.