Long-lived core-hole excited states and high-energy thresholds in stimulated desorption processes: Cl/Si(100)-(2x1)

The valence-electron response to an adsorbate core-hole is studied by means of the configuration-lattice approach in order to include correlation effects as accurately as possible. For the specific case of Cl adsorption on the reconstructed Si(100)-(2 X 1) surface, we find that removal of an electron from the Cl 3s orbital leads to long-lived excited states at 22 and 41 eV, in excellent agreement with the high-energy thresholds found in the stimulated desorption of Cl ions. The first excitation corresponds to a neutral valence-electron distribution(Cl+ desorption) while the second one, which leads to Cl2+, requires transfer of a valence electron from the adsorbate to the semiconductor accompanied by a strong shake-up of electron-hole pairs. These results are compared with those of a previous calculation where the core-hole was not included. (C) 1998 Elsevier Science B.V.