The interaction between small unsaturated hydrocarbon molecules of ${\mathrm{C}}_2{\mathrm{H}}_4$ with a vicinal silicon (001) surface is studied by means of reflectance anisotropy spectroscopy and analyzed with first principles calculations. Our results confirm that ethylene adsorbs without breaking the silicon dimers. Comparison of theoretical optical spectra with experimental data shows that the ${\mathrm{C}}_2{\mathrm{H}}_4$ 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.

• Received 8 November 2007

DOI:https://doi.org/10.1103/PhysRevB.77.125337