Adsorption of small hydrocarbon molecules on Silicon surfaces: ethylene on Si(001)

The interaction between small unsaturated hydrocarbon molecules of C 2 H 4 with a vicinal silicon 共001兲 surface is studied by means of reflectance anisotropy spectroscopy and analyzed with first principles calcula- tions. Our results confirm that ethylene adsorbs without breaking the silicon dimers. Comparison of theoretical optical spectra with experimental data shows that the C 2 H 4 molecules lay on top of the silicon dimers from low to high coverage. This occurs even though, from a purely energetic point of view, a bridge configuration would be favorable at 1 monolayer coverage.