Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 75: Organic/bio Molecules on Metal Surfaces VI
O 75.6: Vortrag
Donnerstag, 14. März 2013, 17:15–17:30, H38
Investigation of the influence of hydrogen bonding on the self-assembled molecular adsorbate structure and manipulation of the electronic structure of tetra(p-hydroxyphenyl)porphyrin — •Lars Smykalla1, Michael Hietschold1, Carola Mende2, and Heinrich Lang2 — 1Chemnitz University of Technology, Institute of Physics, D-09107 Chemnitz, Germany — 2Chemnitz University of Technology, Institute of Chemistry, D-09107 Chemnitz, Germany
Combining scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), photoemission spectroscopy (PES) and density functional theory (DFT), we present a thorough study of the adsorption of tetra(p-hydroxyphenyl)porphyrin (H2THyPP) on crystalline metal substrates. The observed molecular arrangements on Au(111) and the more anisotropic Ag(110) are explained in terms of epitaxy and intermolecular weak hydrogen bonding. Furthermore, the influence of the substrates on the electronic structure of the adsorbed molecules is discussed. The electronic states of the molecule are studied with high spatial resolution using voltage-dependent STM and STS in ultra-high vacuum, whereby two different kinds of molecular appearances at constant voltage in a monolayer are observed. Further, we are able to switch the molecular contrast of single molecules under the STM tip by voltage pulses. To understand the nature of this change in electronic structure of the molecule we applied density functional theory calculations, which indicate that we find on the surfaces the free-base H2THyPP as well as its deprotonated form (without the two hydrogen atoms in the center of the molecule).