Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 56: Metal substrates: Adsorption of organic / bio molecules III
O 56.5: Vortrag
Mittwoch, 28. März 2012, 17:45–18:00, A 053
Perylene derivative on Au(111): Influence of a large built-in dipole on molecular assembly and work function — •Jens Niederhausen1, Heith Kersell2, Henrike Wonneberger3, Saw-Wai Hla2, Jürgen P. Rabe1, Klaus Müllen3, and Norbert Koch1 — 1Humboldt- Universität, Institut für Physik, Berlin, Germany — 2Ohio University, Physics & Astronomy Department, Athens, USA — 3Max Planck Institut für Polymerforschung, Mainz, Germany
The anhydride- and diphenylamine-functionalized perylene derivative 9-(bis-p-tert-octylphenyl)-amino-perylene-3, 4-dicarboxy anhydride (ID28) is expected to exhibit a dipole moment as large as 12.2 Debye [1]. When evaporated on Au(111) in ultrahigh vacuum, ID28 molecules adopt a flat-lying conformation in the monolayer regime, as evident by room temperature scanning tunneling microscopy. We analyze the observed packing structures by involving molecule-substrate and molecule-molecule interactions, and the influence of the molecular dipole moment.
The macroscopic surface-normal electrostatic effect of the molecular dipole moment is investigated by ultraviolet photoelectron spectroscopy. The dipole of a monolayer of ID28 molecules shows no significant contribution to the sample work function. However, when going from monolayer to multilayer coverage we find a continuous work function decrease of up to about 1 eV. This is attributed to a preferred orientation of the molecules in multilayers, resulting in a macroscopic dipole pointing away from the sample surface.
[1] T. Edvinsson et al., J. Phys. Chem. C Letters 2007, 111, 15137