Surface phonons on Si(001)/As(2x1)

We present results of phonon calculations for the Si(001)/As(2x1) surface u sing the adiabatic bond-charge model. It is found that this surface is char acterized by two pronounced peaks in the phonon density of states. One of t hese lies below the bulk continuum at the zone edges and is due to surface acoustic waves involving vibrations of the As atoms. The second of these li es at the bulk acoustic-optical boundary and is related to the vibrations o f the symmetric As-As dimer against the substrate. (C) 1999 Elsevier Scienc e B.V. All rights reserved.