Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 78: Metal substrates: Adsorption of organic / bio molecules IV
O 78.5: Vortrag
Donnerstag, 29. März 2012, 17:00–17:15, A 053
The role of molecular orbitals in scanning tunneling induced luminescence — •Christoph Große1, Theresa Lutz1, Christian Dette1, Alexander Kabakchiev1, Klaus Kuhnke1, Uta Schlickum1, and Klaus Kern1,2 — 1Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany — 2Institut de Physique de la Matière Condensée, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
The plasmonic light spectrum of pristine metals excited by scanning tunneling microscopy (STM) can be affected in many different ways by the adsorption of organic molecules. In this study we elucidate the role of molecular orbitals in the light emission process and employ STM to investigate the optical and electronic properties of individual fac-Ir(ppy)3 molecules on top of a C60 monolayer on Ag(111). In this binary system, the C60 monolayer acts as a molecular decoupling layer. Compared to this, the light excitation on the Ir(ppy)3 molecules increases locally by half an order of magnitude due to a more efficient excitation of tip induced plasmons. Mapping the molecular orbitals by differential conductance (dI/dV) images reveals three distinguishable molecular orbitals. A comparison of their shape with sub-molecular resolved light excitation maps shows a clear correlation between the light enhancement and the orbital closest to the Fermi energy of the substrate.