Dresden 2011 – scientific programme
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O: Fachverband Oberflächenphysik
O 3: Metal substrates: Adsorption of organic / bio molecules I
O 3.1: Talk
Monday, March 14, 2011, 11:15–11:30, PHY C213
Electronic structure of a graphene quantum well system: highly ordered coronene and hexa-peri-hexabenzocoronene films on Ag(111) — •Michael Wießner1, Sofía Rodríguez1, Johannes Ziroff1, Sophia Huppmann1, Frank Forster1, Peter Puschnig2, Achim Schöll1, Lukas Dössel3, Klaus Müllen3, and Friedrich Reinert1 — 1Universität Würzburg, Experimentelle Physik VII, D-97074 Würzburg — 2Chair of Atomistic Modelling and Design of Materials, University of Leoben, 8700 Leoben, Austria — 3MPI für Polymerforschung, Ackermannweg 10, D-55128 Mainz
We present angular resolved photoemission measurements of highly ordered monolayer thin films of coronene and hexa-peri-hexabenzocoronene (HBC) on the single-crystalline Ag(111) surface. Coronene and HBC molecules can be viewed as finite pieces of a graphene layer containing 7 and 13 honeycomb rings, respectively, terminated by hydrogen atoms. Thus, the photoemission signal in these systems can be explained by the formation of quantum well states derived from graphene wave functions which are laterally confined by the spatial extension of the molecules. We also calculated the electronic structure of coronene/HBC by density functional theory (DFT) assuming a free molecule. The fourier-transformed molecular orbitals are shown to reproduce the angle dependent intensity distribution thereby providing a tool to identify different types of orbitals. In conclusion, the solid state derived quantum well states as well as the molecular based DFT orbitals are both applicable to explain the electronic structure of extended aromatic molecules.