Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 30: Metal substrates: Adsorption of organic / bio molecules IV

O 30.7: Vortrag

Mittwoch, 25. März 2009, 12:00–12:15, SCH A118

A quantitative model for the monolayer growth of hydrocarbons on noble metals: HBC on Ag(111) and Au(111) — •Christian Wagner, Daniel Kasemann, Moritz Esslinger, Roman Forker, Christian Golnik, and Torsten Fritz — Institut für Angewandte Photophysik, TU-Dresden, George-Bähr-Str. 1, 01069 Dresden

In our contribution we compare the growth of hexa-peri-hexabenzocoronene (HBC) on Ag(111) and Au(111) for monolayer (ML) and sub-ML coverage[1,2]. Despite the always present attractive van der Waals force we observe a net repulsive interaction between individual HBC molecules on the Au(111) surface, resulting in a complex growth behavior: Unlike the situation on Ag(111) no lattice epitaxy is observed for HBC MLs on Au(111) in the predominant phase. Instead, we find a coverage dependent lattice constant (between 13.6 Å and 14.7 Å). Including coulomb and van der Waals forces as well as Pauli repulsion (by the respective OPLS force fields) between the molecules on one hand, and the influence of the metal substrates, namely attractive binding, mirror charges and even a screening of the van der Waals attraction on the other hand, we propose a quantitative model of the interaction potential of HBC on both metals that can be fitted to the experimental results and is indeed able to explain all findings with reasonable values for the parameters used. Furthermore, we can assign the orientation of HBC domains on Au(111) to the interaction with the surface reconstruction pattern.

[1] H. Proehl et al. Phys. Rev. B 63, 205409 (2001)

[2] P. Ruffieux et al. J. Am. Chem. Soc. 129, 5007 (2007)