Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)

O 24.68: Poster

Mittwoch, 26. März 2003, 14:30–17:30, P1

Chemical patterns in a thiolate monolayer analyzed by SFG microscopy — •Dominik M.P. Hoffmann, Klaus Kuhnke, and Klaus Kern — MPI fuer Festkoerperforschung, Heisenbergstr. 1, D-70569 Stuttgart

IR-visible sum-frequency generation (SFG) microscopy allows the chemically selective imaging of interfaces by tuning the IR-beam to distinct vibrational transitions e.g. of adsorbates[1]. It provides in-situ information about chemical composition, molecular order and coverage at surfaces and buried interfaces by means of vibrational and electronic contrast. We apply a sum-frequency microscope (SFM) developed to image non-transparent surfaces at oblique angles[2]. A pattern of octadecanthiolate is created on gold substrates by means of micro-contact printing. The dimensions of the thiolate pattern are in the micrometer range. Subsequently mercaptohexadecanoic acid is adsorbed for 20 minutes from solution. The resulting chemical pattern is analyzed by sum-frequency microscopy. By taking SFG images at different IR wavelengths and by evaluating the chemical contrast the two thiolates can be discriminated. Additionally, information about the thiolate density, the functional groups and the molecule backbone is obtained. The results are discussed with respect to the properties of pure thiolate phases.