ANISOTROPIC AND POLARIZATION EFFECTS IN RAMAN-SCATTERING IN POROUS SILICON

The polarized Raman scattering from porous silicon in the region of th e fundamental optical phonon is shown to reveal marked anisotropic beh aviour: its strength, frequency shift and line shape are markedly affe cted by the particular choice of scattering geometry. These effects ar e discussed within the framework of the standard phonon confinement mo del, also taking into account the partial breakdown of the polarizatio n selection rules and the dispersion of the longitudinal optical and t ransverse optical phonon branches. The observed effects can be at leas t qualitatively understood by invoking the anisotropy of the phonon di spersion branches, whose relative contribution to the Raman signal var ies with the polarization geometry and (possibly) with the sample morp hology.