Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 77: Electronic Structure and Spin-Orbit Interaction III
O 77.12: Vortrag
Donnerstag, 14. März 2013, 18:45–19:00, H33
Long range charge transfer and electrostatics at a molecular heterojunction on a metal surface — •Patrick Amsalem1, Jens Niederhausen1, Andreas Wilke1, Georg Heimel1, Raphael Schlesinger1, Stefani Winkler1, 2, Antje Vollmer2, Jürgen P. Rabe1, and Norbert Koch1,2 — 1Humboldt-Universität zu Berlin, Institut für Physik, Berlin, Germany — 2Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, BESSY II, Berlin, Germany
Understanding the energy level alignment (ELA) at organic heterostructures grown on conductive electrodes is of major importance for improving organic-based devices. In this work, the ELA at an electron acceptor molecule (C60) / organic spacer (alpha sexithiophene, 6T) / Ag(111) interface is investigated as a function of the 6T thickness (one and two monolayers) by means of photoelectron spectroscopy. The formation of an interface dipole with similar magnitude is found for the two studied systems. Valence band and core level measurements reveal that these interface dipoles result from an integer electron transfer from the metal towards the C60 molecules, through the 6T film [1, 2]. Consistently, the total amount of electrons transferred to the C60 film is found to decrease with increasing 6T thickness. Also, a potential drop within the 6T is observed. These findings are quantitatively addressed by electrostatic considerations to entangle the effect of dipole-dipole interactions and potential drops observed when the interface is formed. [1] P. Amsalem, et al., J. Phys. Chem. C 115, 17503 (2011) [2] J. Niederhausen et al., Phys. Rev. B 86, 081411 (R) (2012)