Brillouin scattering from pseudosurface acoustic waves in (111) silicon

Brillouin scattering from generalized surface acoustic waves and pseudosurf ace acoustic waves propagating on the (111) free surface of single crystal silicon was investigated. The dependence of the phase velocities of the gen eralized and pseudosurface modes on their propagation direction, measured r elative to the [110] direction, was determined. It is found that while the measured velocities of the pseudosurface waves exhibit a similar dependence as that of the theoretical velocities, they are systematically lower than the latter by 4%, a discrepancy which cannot be fully accounted for by expe rimental uncertainties. (C) 1999 Elsevier Science Ltd. All rights reserved.