Hamburg 2001 – wissenschaftliches Programm

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O: Oberflächenphysik

O 9: Organische Dünnschichten und Festkörper

O 9.9: Vortrag

Montag, 26. März 2001, 18:15–18:30, B

Characterization of aliphatic and aromatic self-assembled monolayers by high resolution photoelectron spectroscopy — •Karin Heister¹, Lars Johansson², Michael Zharnikov¹, and Michael Grunze¹ — ¹Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany — ²Department of Physics, Karlstad University, S-65188 Karlstad, Sweden

Synchrotron-based high resolution X-ray photoelectron spectroscopy was applied to monitor the formation of self-assembled monolayers (SAMs) of alkanethiols (AT) and biphenylthiols on Au and Ag. Pronounced chemical shifts in the adsorbate- and substrate-related photoemission lines indicate a strong thiolate-metal bond upon the SAM formation. Only one sulfur species was found in all investigated SAMs. Conclusions on the heterogeneity of the adsorption sites and adsorption geometry could be drawn. Significant final state effects in the C 1s photoemission have been found for both the aliphatic and aromatic SAMs. Additionally, the damage in AT SAMs on Au caused by soft X-rays was investigated. The observed changes in AT SAMs and, in particular, the appearance of a new, irradiation-induced sulfur species are identical to those caused by electron bombardment, implying that most of the damage is produced by the photo- and secondary electrons. The irradiation-induced sulfur species is identified as a dialkylsulfide distributed within the AT film. Only minutes of monochromatized X-ray irradiation at an undulator beamline destroy the AT adlayer completely.