Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 37: Metal substrates: Adsorption of organic / bio molecules IV
O 37.1: Talk
Tuesday, March 23, 2010, 15:00–15:15, H36
Structural dependence of metal organic interface state dynamics studied with 2PPE — •Manuel Marks1, Christian H. Schwalb1, Andreas Namgalies1, Sönke Sachs2, Achim Schöll2, Friedrich Reinert2, Eberhard Umbach2, and Ulrich Höfer1 — 1Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, D-35032 Marburg — 2Universität Würzburg, Experimentelle Physik II, D-97074 Würzburg
Time- and angle-resolved 2-photon photoemission (2PPE) has proven to be a powerful experimental approach to study the electron dynamics at metal organic interfaces. With adsorption of the first monolayer (ML) PTCDA on Ag(111) an unoccupied strongly dispersing interface state (IS) emerges at 0.6 eV above the Fermi Level EF [1]. Also for 1 ML NTCDA/Ag(111) a similar unoccupied state arises at 0.37 eV above EF. The respective inelastic electron lifetimes of 54 fs and 110 fs indicate that the states have a significant overlap with the metal substrate and mainly originate from an upshifted Shockley surface state. We systematically studied the disordered precursor phase of the PTCDA monolayer [2]. For this interface a non-dispersing unoccupied state at 0.45 eV above EF can be observed that has an electron lifetime of 63 fs. The influence of the adsorbate morphology and the origin of this non-dispersing feature will be discussed. Either the disorder leads to a localization of the surface state or the signal stems from a molecular state shifted in energy due to the chemical interaction.
[1] C. H. Schwalb et al., Phys. Rev. Lett. 101, 146801 (2008)
[2] L. Kilian et al., Phys. Rev. Lett. 100, 136103 (2008)