Phonon spectrum and density of states on GaAs(001)-beta(2)(2x4)

Abstract

We have studied the lattice dynamics of the GaAs(001)-beta(2)(2x4) surface by employing two theoretical methods: an ab initio pseudopotential method and a phenomenological adiabatic bond-charge method. Both methods predict a number of surface localized phonon modes. Most of these modes are found to lie at similar energy locations from both methods. However, the two methods produce eigenvectors of some of the modes which are at variance with each other. Possible reasons for such differences are outlined. Particular emphasis has been laid on the discussion of the highest surface phonon mode, which lies above the bulk continuum. A brief discussion of the role of this mode in examining surface reactions has also been provided.