Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Oxides and insulators III

O 17.8: Vortrag

Dienstag, 24. März 2009, 12:15–12:30, SCH A01

An Azobenzene Derivate on NaCl/Ag(111): Surface Structure, Molecule Adsorption, and Electron-Induced Switching — •Ali Safiei, Jörg Henzl, and Karina Morgenstern — Leibniz University of Hannover, Institute of Solid State Physics, Appelstraße 2, 30167 Hannover

Thin NaCl films on metallic substrates offer the possibility of investigating the conformational, mechanical and electronic structure and thus functionalities of molecules with low coupling to the substrate. We first studied the growth of NaCl islands by scanning tunnelling microscopy and spectroscopy on the clean Ag(111) surface. On this surface the islands grow epitaxially in double layers, are atomically flat and nearly defect-free. Spectroscopic dI/dV measurements show that the surface state of Ag on NaCl double layer is shifted to higher energies than on the pure Ag(111) surface. Amino-nitro-azobenzene molecules (ANA) are adsorbed on the NaCl islands at very low temperatures. We found the trans-configuration of ANA on the ultra-thin insulting layers and realized a reversible switching process by electron-induced manipulation. In contrast to the switching processes on Au(111) [1], these conformational changes resemble the trans-cis isomerisation of the ANA molecule in the gas phase. The reason is that the molecules on NaCl islands are less coupled to the substrate. The shift of the surface state of Ag on NaCl, the switching process and the energy barrier of the reversible switching will be discussed in this talk.

[1] Jörg Henzl, Michael Mehlhorn, Heiko Gawronski, Karl-Heinz Rieder, Karina Morgenstern, Angew. Chem. Int. 45 (2006) 603-606.