A brief review of the electronic properties of semiconductor reconstructed surfaces was given, the case of Si(111)2 x 1 being considered in detail. Optical transitions between surface state bands show a large anisotropy that strongly supports the so called chain model of the reconstruction. Results on the dependence of such transitions on temperature show a considerable electron-lattice interaction at the surface. An Einstein mode with energy around 10meV, analogous to that found with He scattering, seems necessary to explain the observed results. The shape of the spectrum and the number of phonons involved suggest a localized process. Discussion of the results and speculations on a surface polaron will be presented.

Electronic Properties and the Dynamics of Reconstructed Semiconductor Surfaces. G.Chiarotti: Physica Scripta, 1987, T19B, 387-90