Angle-resolved electron-energy-loss study of Al/Si(111)

Abstract

We have performed a high-resolution electron-energy-loss study of the Si(111)-(~3x~3)R30':Al surface and have measured the dispersions of several surface phonons along the I'K direction. We interpret these using two different simple lattice dynamical models, both employing force constants from an ab initio electronic-structure calculation of Northrup. The first yields quantitative information at q = 0; the second is a semiquantitive estimate of the dispersion. These models have no adjustable parameters. The good agreement with the experiment for most of the observed modes indicates that a single theory can explain both the electronic structure and vibrational modes of this surface and also illustrates both the usefulness and limitations of simple models of lattice dynamics.

High resolution electron energy loss studies of surface vibrations. Progress report, November 1, 1990--May 1, 1993

“…This study was restricted to zero momentum transfer (/_) and it was found that certain phonon energies were in agreement with calculations by Northrup [7]. Recently, we have measured the dispersion of these modes along a high symmetry axis (/_/() of the SBZ [8]. We have shown that by use of force constants from the ab initio electronic structure calculation of Northrup it is possible to account for the mode dispersion in a semi-_uantitative way, with no adjustable parameters.…”

Photoelectron diffraction of the Si(111)-(3×3)R30°-Ga surface: Local atomic structureand vibrational correlation

“…22 The mode is characteristic of the Si͑111͒ surface having T 4 adatoms. 23,24 As far as high-energy photoelectron is concerned, forwardscattering is dominant, and only the wave emitted toward the scatterer contributes to the intensity. Therefore, the parity of the photoelectron wave function has no influence upon the intensity distribution.…”