Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 58: Poster Session III (Solid/liquid interfaces; Metals; Semiconductors; Oxides and insulators)

O 58.17: Poster

Wednesday, March 28, 2012, 18:15–21:45, Poster B

Adsorption dependent charge state of self-assembled donor-acceptor complexes on Au(111) — •Tobias R. Umbach, Isabel Fernández-Torrente, Jose I. Pascual, and Katharina J. Franke — Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany

The redistribution of charge between organic species and surfaces plays a key role for tuning the electronic functionality of molecular organic compounds on metal surfaces. We investigate self-assembled monolayers of 11,11,12,12-tetracyanonaphtho-2, 6-quinodimethane (TNAP) mixed with sodium (Na) on a Au(111) surface by low temperature scanning tunneling microscopy and spectroscopy (LT-STM, LT-STS). Successive deposition of TNAP and Na leads to the formation of an ordered windmill structure of TNAP and Na. The molecules close to the soliton lines are single charged accompanied by a Kondo resonance observed in STS transport experiments. In contrast, all other TNAP molecules show no Kondo resonance. The adsorption site dependent charge state of the TNAP molecules in the Na-TCNQ layer is an indication for different alignments of the molecular orbitals and therefore variations of the charge transfer process.