The surface profile of charge of Si(111) (7 x 7) obtained with He scattering

Theoretical calculations in good agreement with experimental data of He scattering from Si(111) (7 x 7) by Cardillo and Becker are presented. From the analysis, it is concluded that (i) the charge distribution in the surface is disposed in two terraces, each one occupying ''half'' of the reconstructed (7 x 7) unit cell and separated by a distance of 3.05 A perpendicular to the surface. The profile of charge on the terraces presents peak to valley oscillations smaller than approximately 0.3 A, (ii) there exists a shallow attractive well with a depth D approximately equal to - 4.2 meV and two bound states epsilon0 approximately equal to - 3.8 meV and epsilon1 approximately equal to - 0.7 meV are inferred. The ''consistency'' of the analysis with the proposed models for the (7 x 7) reconstruction is discussed. (author)