Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 38: Adsorption V

O 38.10: Talk

Thursday, March 30, 2006, 17:15–17:30, TRE Phys

Isomerization of an azobenzene derivative on Au(111) by scanning tunneling microscopy — •Micol Alemani, Leonhard Grill, Karl Heinz Rieder, and Francesca Moresco — Inst. für Exp.physik, FU Berlin, Arnimallee 14, D-14195 Berlin

Azobenzene molecules are of great interest because they have in the gas phase two stable isomers (cis and trans) and can switch reversibly from one configuration to the other by photo-excitation. An azobenzene derivative, equipped with four tert-butyl groups, has been investigated on Au(111) with a scanning tunnelling microscope (STM) at low temperature (5K).

The molecules result mobile after preparation at room temperature and form islands. From the STM images, the exact molecular orientation and configuration have been extracted. All the molecule are found in the trans configuration, as it is in the gas phase the more energetically favoured one.

By applying voltage pulses with the STM tip on molecular islands, the isomerization of single molecules from the trans configuration to the cis and backwards has been realized. The process is characterized by changing the applied voltage. A model is proposed for the cis isomer adsorbed on the surface which is in accordance with its chemical properties.