Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 78: Metal substrates: Adsorption of organic / bio molecules IV

O 78.2: Vortrag

Donnerstag, 29. März 2012, 16:15–16:30, A 053

Single-molecule spectroscopy of terthiophene adsorbed on Au(111): electronic and vibronic properties — •Berndt Koslowski, Norbert Maurer, Anna Tschetschetkin, and Paul Ziemann — Institute of Solid State Physics, University of Ulm, D-89069 Ulm, Germany

Because of their expedient properties and their diversity, oligo- and polythiophenes are among the most investigated organic semiconductors. We investigated the adsorption of terthiophene molecules (3T) on Au(111) at low temperature by means of Scanning Tunneling Microscopy and Spectroscopy. 3T adsorbs preferentially in the fcc regions and orients perpendicularly to the soliton walls of the herringbone reconstructed Au(111). Tunneling spectroscopy in the center of the molecule shows the broad LUMO of the molecule at +2.3 eV on a background resembling properties of the gold surface. The HOMO was determined to lie at -1.3 eV leaving the optical gap unchanged as compared to the gas-phase molecule. dI/dV maps reveal a very inhomogeneous distribution of the LUMO/HOMO across the molecule indicating a significant interaction of molecular states with the substrate [1]. By inelastic electron tunneling spectroscopy we find very rich vibrational spectra on the molecules containing more than 30 modes. We analyze the vibronic spectrum and compare it to spectra expected for the free molecules and other experimental results. [1] Koslowski et al., Beilstein J. Nanotechnol. 2, 561-568 (2011).