LOW-ENERGY VIBRATIONS AT THE INSB(110) SURFACE

We present a study of low-energy vibrations at the InSb(110) surface a long the <(Gamma Y)over bar> direction. Surface phonons have been meas ured by He inelastic scattering and a theoretical analysis has been pe rformed by means of first-principles calculations. We have been able t o distinguish the surface acoustic mode above the Rayleigh wave and to identify a surface resonance and an optical surface mode at higher en ergy. Theoretical calculations are shown to be in agreement with the d etected phonon dispersion curves except for the surface resonance whic h is found 1 meV higher than calculated.