Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 9: Organic films I
O 9.4: Vortrag
Montag, 27. März 2006, 15:45–16:00, TRE Phys
Novel Tripod Ligands for Prickly Self-Assembled Monolayers — •Tobias Weidner1, Andreas Krämer2, Michael Zharnikov3, Andrey Shaporenko3, Dominik Enders4, Ulrich Siemeling2, and Frank Träger1 — 1Institut für Physik, Universität Kassel, Kassel — 2Institut für Chemie, Universität Kassel, Kassel — 3Angewandte Physikalische Chemie, Universität Heidelberg, Heidelberg — 4Kirchhoff Institut für Physik, Universität Heidelberg, Heidelberg
Self-assembled monolayers (SAMs) consisting of laterally separated and non-interacting functional units are of great current interest in sensor- and molecular electronics applications. We used the new ligands PhSi(CH2SMe)3 (1) and Ph-p-C6H4-Si(CH2SMe)3 (2) to prepare such SAMs on gold. In 1 and 2 the rigid rod type units Ph and Ph-p-C6H4, respectively, are connected to the central Si atom at the vertex of the tripodal binding unit that can be anchored on the surface with three instead of a single binding site via thioether head groups. In particular, owing to the relative size of the binding unit, the SAMs are expected to exhibit considerable void space between individual Ph and Ph-p-C6H4 units which protrude from the surface.
Film formation was investigated in situ by optical second harmonic generation and ellipsometry, revealing a two-step process. SAMs of 2 were further investigated by ex situ methods, viz. high-resolution XPS (HRXPS), IR-spectroscopy, and STM. The most important results are as follows: HRXPS showed three different binding states of sulfur. Dense packing of the tripodal anchor groups on the surface has been verified with a substantially lower density of the biphenyl pricks.