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O: Fachverband Oberflächenphysik
O 59: Poster Session II (Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: arrays; Nanostructures at surfaces: Wires, tubes; Nanostructures at surfaces: Other; Plasmonics and nanooptics; Metal substrates: Epitaxy and growth; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsoprtion of organic / bio molecules; Metal substrates: Adsoprtion of inorganic molecules; Metal substrates: Adsoprtion of O and/or H; Metal substrates: Clean surfaces; Density functional theory and beyond for real materials)
O 59.84: Poster
Wednesday, March 24, 2010, 17:45–20:30, Poster B1
Substrate- and temperature-dependent adsorption studies of azobenzene molecules. — •Alex Krüger1, Marten Piantek1, Matthias Bernien1, Felix Hermanns1, Jorge Miguel1, Klaus Hermann2, and Wolfgang Kuch1 — 1Freie Universität Berlin, Institut für Experimentalphysik — 2Theory Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft
The adsorption of dimetacyano-azobenzene (DMC) evaporated onto Cu(100) and Au(111), as well as on CoO/Ag(100), was studied at different substrate temperatures in order to ascertain the influence of substrate and coverage. Angle-dependent NEXAFS spectroscopy was used to resolve the adsorption geometry of the molecules. By XPS the formation of additional bonds between the molecules and surface was investigated. For the adsorption on Au(111) at room temperature (RT), and on Cu(100) at 150 K, we find the molecules physisorbed in a planar conformation parallel to the surface. In the case of molecules adsorbed at 100 K on CoO/Ag(100), we observe a change in the angle dependence of the π* resonances of the N-K edge NEXAFS. After annealing the Cu(100) substrate to RT, the angle dependence and intensity of the π* resonances change significantly. From the peak assignment derived from DFT-based simulation of the NEXAFS spectra, we conclude that chemisorption takes place at the azo-nitrogen on Cu(100) at RT, whereas a mixed phase of physisorbed and chemisorbed molecules is found on CoO/Ag(100) at 100 K, and on Cu(100) at 150 K. In contrast, only the physisorbed phase was found for DMC on Au(111) at RT. This work has been supported by Sfb 658.