Abstract
Conduction-band surface-plasmon excitations are seen to contribute to the quasielastic scattering of low-energy electrons from clean Si(111)7×7 surfaces. We have analyzed these observations by means of a multiple-scattering theory and show that these excitations are localized below the surface space-charge layer. A comparison of the deduced surface-charge-density profile is in good agreement with the Fermi-level pinning at this surface.