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TT: Fachverband Tiefe Temperaturen
TT 35: TR: Nanoelectronics III: Molecular Electronics 1
TT 35.11: Vortrag
Donnerstag, 25. März 2010, 16:45–17:00, H21
Influence of substituents on the transport properties of molecular junctions — •Falco Hüser1, Fabian Pauly1, and Gerd Schön1,2 — 1Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany — 2Institut für Nanotechnologie, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany
We study by DFT-based methods the correlation between the Hammett constant and the transport properties of single-molecule junctions, i.e. their conductance and thermopower [1]. Motivated by recent experiments [2,3,4], we focus on a large variety of benzenediamines [2] and of benzene-alkane-dithiols [3].
Electron-donating side-groups shift the conducting molecular orbitals up and increase the conductance and thermopower for the hole-conducting molecules, while electron-accepting side-groups have the opposite effect. By means of a single-level model, we relate these effects to properties of the isolated molecules. Relative variations are found to be in good agreement with the measurements.
Going beyond the experiments, we show how the influence of the substituents can be diminished by alkyl spacers and reestablished by alkenyl spacers.
[1] F. Hüser, F. Pauly, G. Schön (submitted).
[2] L. Venkataraman et al., Nano Lett. 7, 502 (2007).
[3] E. Leary et al., Chem. Commun. 38, 3939 2007.
[4] K. Baheti et al., Nano Lett. 8, 715 (2008).