Brillouin spectroscopy of porous Si (π-Si) formed on p-type (100) Si has revealed two acoustic-phonon peaks associated with the surface and film modes of the thick porous slab. They exhibit relatively large peak widths that are attributed to fractons. Longitudinal wave guiding is enhanced in high porosity π-Si due to its very low sound velocities compared with Si. Unlike opaque semiconductors where ripple scattering is dominant, the elasto-optic contribution to the scattering mechanism is found to be significant in π-Si. Both phonon velocities show appreciable negative dispersion due to a porosity gradient.
No takes yet. Share an insight, caveat, or question.
Lockwood et al. (1999) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: