Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 59: Poster Session II (Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: arrays; Nanostructures at surfaces: Wires, tubes; Nanostructures at surfaces: Other; Plasmonics and nanooptics; Metal substrates: Epitaxy and growth; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsoprtion of organic / bio molecules; Metal substrates: Adsoprtion of inorganic molecules; Metal substrates: Adsoprtion of O and/or H; Metal substrates: Clean surfaces; Density functional theory and beyond for real materials)

O 59.91: Poster

Wednesday, March 24, 2010, 17:45–20:30, Poster B1

Scanning Tunneling Microscopy and Spectroscopy of Phthalocyanine Molecules on Insulating Films — •Christof Uhlmann, Ingmar Swart, Tobias Sonnleitner, and Jascha Repp — Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany

Ultrathin insulating films on metal substrates can be used to electronically decouple individual molecules from the metallic substrate. As electrons can still tunnel through the films, scanning tunneling microscopy can be used to characterize these molecules. This geometry represents a double-barrier tunneling junction, in which at the resonances in conductance spectra, an electron is temporarily added to or removed from the molecule. Here we present a study of Cu-phthalocyanine molecules on different substrate systems. For a neutral Cu-phthalocyanine molecule the lowest unoccupied molecular orbital (LUMO) and the LUMO+1 are degenerate. By varying the substrate system, and thereby also varying the work-function, it is possible to permanently charge the molecules. Consequently, either the former LUMO or the former LUMO+1 is occupied with one electron. Due to the Jahn-Teller effect, the degeneracy of these orbitals is lifted. This manifests itself in a lowering of the symmetry as deduced from STM images.