Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 6: Metal substrates: Adsorption of organic / bio molecules I

O 6.1: Talk

Monday, March 22, 2010, 11:15–11:30, H36

Phase boundaries in organic adlayers – a quantitative video-STM study — •Michael Roos, Harry E. Hoster, and R. Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany

Bis(terpyridine)derivatives (BTP) form highly ordered hydrogen-bonded networks on different substrates at solid surfaces [1,2]. Using time resolved scanning tunneling microscopy (STM), we have studied dynamic phenomena in such adlayers on Ag/Ru(0001) at room temperature. BTP molecules on Ag/Ru(0001) form coverage dependent networks with different hydrogen bonding configuration. At low coverages, a parallel chain structure (PCS) is formed in coexistence with a two-dimensional admolecule gas. At higher coverages, domains of a locally more densely packed quasi quadratic network (QQN) are formed [2]. Time resolved STM imaging at QQN|PCS phase boundaries reveals a continuous exchange of molecules between both phases as indicative for a dynamic equilibrium. Based on a statistical evaluation of the STM sequences, we show that the anisotropy of the molecule-molecule interactions is not only reflected in the periodic structures of the 2 adlayers, but also in the probability of different types of local rearrangements at the phase boundary.
[1] M. Roos et al., Phys.Chem.Chem.Phys. 9, 2007, 5672.
H. E. Hoster et al., Langmuir 23, 2007, 11570.