Quasielastic light scattering in silicon

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Abstract
An investigation of the origin of quasielastic light scattering from silicon surfaces, first observed by Sandercock (1972, 1978) is described. Measurements have been made of the dependence of the quasielastic spectrum upon temperature, wavevector, doping level, and polarisation and intensity of incident light. The results rule out the possibilities of scattering by free electrons or by entropy fluctuations in a collision-dominated phonon regime. A simplified calculation suggests that two-phonon difference scattering may be the origin of the observed spectrum with the main contribution coming from pairs of optic phonons on the same dispersion branch.