Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)
O 27.120: Poster
Dienstag, 24. März 2009, 18:30–21:00, P2
Dynamics of electron transport at the PTCDA/Ag(111)-interface studied with time-resolved 2PPE — •Christian Schwalb1, Sönke Sachs2, Manuel B. Marks1, Achim Schöll2, Eberhard Umbach2,3, and Ulrich Höfer1 — 1Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, D-35032 Marburg — 2Universität Würzburg, Experimentelle Physik II, D-97074 Würzburg — 3Forschungszentrum Karlsruhe, D-76021 Karlsruhe
Time-resolved two-photon photoemission (2PPE) is able to provide very detailed information about the electronic structure and the dynamics of electron transfer processes of well-ordered interfaces between organic semiconductors and metals. As a model system we have investigated thin epitaxial PTCDA films on Ag(111). A dispersing unoccupied state with an effective electron mass of 0.39 me at the Γ-point emerges 0.6 eV above the metallic Fermi level EF. Its short lifetime
of 55 fs is a clear indication that this state has a strong overlap with the metal and essentially originates from an upshift of the Shockley surface state of the Ag substrate [1]. In order to investigate the role of the interface state for charge carrier injection, we populate the LUMO of PTCDA in films of varying thickness and simultaneously record fluorescence and photoemission spectra. A long lived component observed in the 2PPE signal close to EF clearly correlates with film thickness and fluorescence lifetime.
[1] C.H. Schwalb et al., Phys. Rev. Lett. 101,
146801 (2008)