Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 38: Adsorption an Oberflächen III

O 38.4: Vortrag

Donnerstag, 11. März 2004, 16:30–16:45, H38

Nitrile-functionalized molecules adsorbed on Si(001)-2x1 — •Ralf Funke1, Stefan Kubsky1, Francois Rochet2, Sylvie Rangan2, Holger Stein1, and Ulrich Köhler11Experimentalphysik / Oberflächenphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany — 2Laboratoire de Chimie Physique Matière et Rayonnement, Université Pierre et Marie Curie, Paris, France

A controlled adsorption behaviour of organic molecules on silicon is essential for the deposition of organic layers as a first step for molecular electronics. The adsorption of acrylonitrile and allylnitrile was studied using STM at 300K and at 90K. These results were correlated with X-ray photoemission and absorption spectroscopy data. Both molecules adsorb in a non-dissociative mode. For low coverage a single adsorption site was found. In the case of acrylonitrile the molecule bridges two adjacent silicon dimer rows inducing a strong local dimer buckling in one of the rows. Bias dependent images and MO calculations are used to determine the adsorption geometry. Time resolved STM images at 90K show a flipping between local configurations of the molecule on a time scale of seconds.

The four C-atoms of allylnitrile bond in a semicircle-like configuration to the silicon atoms of two neighbouring dimers in one dimer row. Whereas in the case of acrylonitrile no long range order in the adsorbate layer was found, the allylnitrile layer shows a (2x2) periodicity. The above results show that despite an identical functional CN-group in a molecule the local bonding to the silicon surface can be completely different.

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