Non-Resonant Formation of H- Ions Near Si(100) Surfaces
Boyan Obreshkov, Uwe Thumm
James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS, USA
We calculate the outgoing fractions of negative hydrogen ions that are normally incident on an unreconstructed Si(100) surface with kinetic energies between 30 and 150 eV . The electronic structure of the substrate is derived from a self-consistent screened Thomas-Fermi-von-Weizsaecker pseudo-potential, including Wang-Teter Si-core-lattice-structure corrections. The orbitals and energies of the electronic states in this potential are obtained by solving Kohn-Sham equations. The dynamics of the transfer of a single electron during the ion-surface collision is studied within a Newns-Anderson model, including image-charge interactions and electron translation factors. We reveal that the formation rate of H- on exit from the surface is determined by the competition of resonant electron loss to the conduction band and non-resonant capture from the valence band into the affinity level of the negative ion, mediated by dangling-bond states and find semi-quantitative agreement with experimental results .
This work was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, and by the National Science Foundation.References:
 B. Obreshkov and U. Thumm, Phys. Rev. A, submitted (May 2007).
 M. Maazouz, et al., Surf. Sci. 398, 49 (1998).
Presented at ISIAC, August 2007 in Crete, Greece.
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