Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 4: Metal substrates: Adsorption of organic / bio molecules I
O 4.1: Vortrag
Montag, 23. März 2009, 11:15–11:30, SCH A118
Molecule-substrate interactions of a strong charge-transfer molecule — •Daniel Wegner1, Stephane Bedwani2, Alain Rochefort2, and Michael F. Crommie1 — 1University of California at Berkeley and Lawrence Berkeley National Laboratory, Berkeley, USA — 2Ecole Polytechnique de Montreal, Canada
Molecules containing multiple cyano groups such as tetracyanoethylene (TCNE) or tetracyanoquinodimethane (TCNQ) represent the archetype of strong electron acceptors. These molecules play a vital role in charge-transfer complexes and metal-organic coordination networks. Potential applications range from nanoscopic templating to molecular electronics and molecule-based magnetism. However, there is still a general lack of information on the properties of these molecules in contact with a conducting surface (e.g., the metallic leads of a single-molecule junction). We have performed scanning tunneling microscopy experiments and first-principles density functional theory calculations of the adsorption of TCNE on the Cu(100) surface. By comparing the experimental results with two different adsorption models, we show that the molecular self-assembly is caused by a strong structural modification of the Cu(100) surface rather than the formation of a coordination network via diffusing Cu adatoms. Surface atoms become highly buckled, and the chemisorption of TCNE is accompanied by a partial charge transfer due to a bonding-backbonding process.