Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 59: Molecular Nanostructures

O 59.9: Vortrag

Donnerstag, 28. Februar 2008, 11:30–11:45, MA 041

Video-STM investigation of the dynamic behavior of bis-terpyridine submonolayers on Ag(111)-oriented films — •Thomas Waldmann, Harry E. Hoster, and R. Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany

We present a quantitative analysis of the dynamic exchange of single molecules between two phases [1] of a bis-terpyridine derivative (2,4'-BTP) [2] adlayer adsorbed on Ag(111)-oriented thin films on Ru(0001). The analysis is based on video-STM measurements in ultra high vacuum at room temperature. The adlayer was produced by evaporation on a highly ordered (111)-oriented Ag film, which leads to the formation of a quasi-quadratic network (QQN) [2, 3]. Via thermal desorption it is possible to create defects in the QQN, which leads to a new disordered phases with a quasi-hexagonal short-range order (QHP). Depending on the BTP coverage 70-90% of the molecules in the QHP are rotating, while the rest exhibits preferred orientations in steps of 30°. At the QQN/QHP phase boundary, we observed molecules jumping back and forth between both phases. From the different probabilities to find the molecules in either phase we estimated the corresponding energy difference via a Boltzmann-approach.

[1] Poster O 18.58

[2] C.Meier et al., J.Phys.Chem.B 109, 21015 (2005)

[3] H.E.Hoster et al., Langmuir 23, 11570 (2007)