Regensburg 2010 – wissenschaftliches Programm

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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 59.95: Poster

Mittwoch, 24. März 2010, 17:45–20:30, Poster B1

Kondo effect on a mixed Na-TCNQ layer — •Tobias R. Umbach, Isabel Fernández-Torrente, Robert Drost, Jose I. Pascual, and Katharina J. Franke — Institut für Experimentalphysik, Freie Universität Berlin, Animallee 14, 14195 Berlin, Germany

Mixing organic molecules with dopant atoms is a key issue in the field of organic electronics, as charge transfer processes may be used to tune the electronic properties of the compound. Here we report, by means of low-temperature scanning tunneling microscopy and spectroscopy measurements (LT-STM, STS), the doping of TCNQ by Na on a Au(111) surface. The addition of NaCl to previously formed TCNQ domains breaks the hydrogen network structure of the pure molecular island, leading to the formation of a new ordered Na-TCNQ phase with a bidimensional *wind-mill*-like structure. This self-assembling provokes a lateral electron transfer from the alkali metal to the organic molecule, inducing the localization of an unpaired spin on TCNQ. This free radical state can be demonstrated by the observation of a Kondo resonance arising in the Na-TCNQ unit cell. By STS we can plot the Kondo intensity of this unpaired spin: the Kondo resonance exhibits a different height along the Na-TCNQ layer, being largest at the center of the *wind-mill*structure and smaller at the center of the molecule.