The authors studied the adsorption-desorption behaviour of Ar and Xe on the Si(111)-(7 x 7) reconstructed surface. Using thermal desorption spectroscopy one could clearly distinguish between adsorption in the monolayer range and higher coverage. Desorption from the second and higher layers show up in a non-saturating desorption peak of zero-order kinetic at lower temperatures while in the monolayer range they observe a saturating behaviour of the desorption rate with a complex structure at higher temperatures. Here the adsorbate-substrate interaction was dominant and different adsorption sites could be resolved demonstrating the rough character of the 7 x 7 reconstruction. This interpretation was confirmed by a controlled in situ change of the 7 x 7 reconstruction using a saturation pre-coverage of atomic hydrogen. The concentration and binding energy of the different binding sites were obtained by fitting a theoretical desorption model to the data. The relevance of the model and alternative models was discussed.

Surface Structure and Thermal Desorption Spectroscopy in Si(111). J.W.Bartha, U.Barjenbruch, M.Henzler: Journal of Physics C, 1986, 19[14], 2459-67