Dresden 2011 – scientific programme
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O: Fachverband Oberflächenphysik
O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)
O 36.15: Poster
Tuesday, March 15, 2011, 18:30–22:00, P4
Substrate- and temperature-dependent adsorption studies of spiropyran molecules — •Alex Krüger1, Marten Piantek1, Ch. Felix Hermanns1, Jorge Miguel1, Matthias Bernien1, Klaus Hermann2, and Wolfgang Kuch1 — 1Freie Universität Berlin, Institut für Experimentalphysik — 2Theory Department, Fritz-Haber- Institut der Max-Planck-Gesellschaft
The adsorption of trimethyl-6-nitrospiropyran, a photoswitch that can be optically switched between its spiropyran (SP) and merocyanine (MC) isomer forms, on Au(111) and Bi(110) single-crystal surfaces was studied as a function of coverage and substrate temperature by near-edge x-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS). For one monolayer on Au(111) at 150 K and room temperature (RT), we find that the molecules are physisorbed in their SP conformation. After annealing the sample to 330 K, the angle dependence and intensity of the N π*-resonances changed, and a chemical shift of the N 1s XPS signal was observed and interpreted as a thermally induced ring-opening reaction of molecules from the SP into the MC form. On Bi(110) the adsorption behavior is similar but the nitro group experiences a chemical modification. Based on a peak assignment derived from DFT simulations of the NEXAFS spectra, this species is interpreted as the ring-opened MC conformer. The ability for conformational switching of the adsorbed molecules was studied by illuminating the sample with UV and visible light. The N K edge NEXAFS spectra showed a significant change after illumination with UV as well as with visible light.