Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)

O 14.16: Poster

Monday, March 27, 2006, 18:00–21:00, P2

Adsorption of acetylene and ethylene on group-IV semiconductor (001) surfaces: results from ab-initio theory — •J. Wieferink, P. Krüger, and J. Pollmann — Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster

A detailed understanding of the adsorption of organic molecules on semiconductor surfaces is a key for their future use in semiconductor devices. We have, therefore, carried out a comparative theoretical study of the adsorption of acetylene and ethylene on (001) surfaces of Si, Ge, and SiC. Optimized structures, adsorption energies and electronic properties have been calculated employing density functional theory.

On Si(001)-(2×1), both acetylene and ethylene adsorb in on top positions above intact symmetric Si–Si dimers. Acetylene molecules may alternatively bridge two Si atoms on two adjacent dimers. Our electronic structure for ethylene on Si(001) is in very good agreement with ARUPS data. The same obtains for our results for ethylene on Ge(001).

In addition we present the first ab-initio results for acetylene and ethylene on SiC. The adsorption behavior of these molecules on Si-terminated SiC(001)-(2×1) is completely different from the adsorption on Si or Ge(001). This is related to the much smaller lattice constant of SiC, as comparered to Si, and to its strong ionicity. For molecular adsorption of ethylene a cross dimer geometry turns out to be most favorable while acetylene prefers a rotated bridge site on SiC(001).