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O: Fachverband Oberflächenphysik

O 58: Poster Session III (Solid/liquid interfaces; Metals; Semiconductors; Oxides and insulators)

O 58.21: Poster

Mittwoch, 28. März 2012, 18:15–21:45, Poster B

Pentacene/Ag(110): A comparison of DFT and GW results with photoemmision data — •Daniel Lüftner¹, Thomas Ules², Georg Koller², Michael G. Ramsey², and Peter Puschnig¹ — ¹Lehrstuhl für Atomistic Modelling and Design of Materials, Montanuniversität Leoben, Franz-Josef-straße 18, A-8700 Leoben, Austria — ²Institut für Physik, Karl-Franzens-Universität Graz, Universitätsplatz 5, A-8010 Graz, Austria

We have prepared a monolayer of pentacene on Ag(110) and studied its valence electronic structure by angle-resolved photoemission spectroscopy. Thereby, an extensive data set of the photocurrent I as a function of parallel momenta (k_x,k_y) and binding energy E_b has been obtained. By comparing this data cube with simulated momentum maps of various pentacene molecular orbitals, we unambiguously identify four molecular states between the Fermi level and the top of the Ag d-band. This allows us to investigate in detail their energetic positions, broadenings, and modifications in orbital shapes upon adsorption. Moreover, we have calculated the electronic structure of different geometric arrangements of pentacene molecules within the framework of density functional theory (DFT) and – on top of that – the G₀W₀ approximation. We show that G₀W₀ corrections greatly improve DFT band gaps and demonstrate that the G₀W₀ gaps are strongly dependent on the local environment of the pentacene molecule, an effect which is absent in DFT orbital energies. Finally, we compare the orbital energies from DFT and G₀W₀ calculations to the experimental values obtaiend for the pentacene monolayer on Ag(110).