Dresden 2006 – scientific programme
Parts | Days | Selection | Search | Downloads | Help
O: Oberflächenphysik
O 25: Organic films II
O 25.3: Talk
Tuesday, March 28, 2006, 16:15–16:30, PHY C213
Self-assembled monolayers of molecular switches - azobenzene carrying alkanethiols on gold — •R. Schmidt1, W. Freyer1, T. Gießel1, K. Herrmann1, H. Prima Garcia1, R. Weber1, and M. Weinelt1,2 — 1Max Born-Institute, Berlin, Germany — 2Freie Universität Berlin, Germany
Alkanethiols form self-assembled monolayers (SAMs), e.g., bound to gold films via the sulphur headgroup and are thus promising candidates for molecular devices. For this purpose the thiols need to be fuctionalized by an appropriate endgroup. We chose azobenzene a cis-trans-conformation switch. Absorption measurements prove that in solution azobenze attached to decanethiols switches reversible upon irradiation at 360 nm and 450 nm.
By NEXAFS-spectroscopy (U41 at BESSY II) we investigated both the azobenzene-decanethiol adsorption geometry and its subsequent change upon irradiation. The layers are well ordered at 90 K, but less ordered at 300 K. Switching seems to be seldom reproducible. However, the temperature dependence of both the adsorption geometry and the switching process makes conceivable a fundamental change of the isomerization energetics at the surface. Autoionization after resonant excitation (N1s, C1s to pi*) reveals strong Resonant-Raman-Auger contributions. Thus charge transfer between azobenzene switch and Au substrate is substantially slowed down by the thiol spacer.