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O: Fachverband Oberflächenphysik
O 42: Organic/bio Molecules on Metal Surfaces IV
O 42.10: Vortrag
Mittwoch, 13. März 2013, 12:45–13:00, H38
Unconventional self-assembled monolayers with unusual properties — David A. Egger1, Ferdinand Rissner1, Oliver T. Hofmann1, Amir Natan2,3, Leeor Kronik2, Georg Heimel4, and •Egbert Zojer1 — 1Institute of Solid State Physics, Graz University of Technology, 8010 Graz, Austria — 2Department of Materials and Interfaces, Weizmann Institute of Science, 76100 Rehovoth, Israel — 3Department of Physical Electronics, 69978 Tel-Aviv University, Tel-Aviv, Israel — 4Institut für Physik, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 6, 12489 Berlin, Germany
We use density-functional theory calculations to show that self-assembled monolayers (SAMs) made from molecules consisting of conjugated distributed dipolar units have unusual properties: * Work-function modifications tuned linearly with the number of repeat units are limited by Fermi-level pinning,[1] where the limitations can be overcome using advanced design strategies.[2] * Collectively induced internal electric fields change the nature of the electronic states within such SAMs in a way strongly reminiscent of the quantum-confined Stark-effect [3] with a closure of the global band-gap beyond a certain number of repeat units. [4] * Moreover, SAMs can be realized that display different polarity of charge transport, in spite of consisting of molecules with virtually identical electronic properties.[5] All these observations can be traced back to collective effects prevalent in such SAMs. [1] Phys.Chem.Chem.Phys., 2010, 12, 4291; [2] Nano Lett. 10, 4369 (2010); [3] J. Am. Chem. Soc. 133, 18634 (2011); [4] Org. El. 13, 3165 (2012); [5] Adv. Mater. 24, 4403 (2012).