Raman microprobe scattering of solid silicon and germanium at the melting temperature

Raman microprobe spectroscopy is used to study c-Si and c-Ge heated to the melting point by a tightly focused cw laser beam. At their respective melting temperatures, the Raman shifts of solid Si and Ge are 481.7±0.4 and 281.4±0.5 ${\mathrm{cm}}^{\mathrm{-}1}$, and the linewidths are 24.3±0.3 and 14.1±0.5 ${\mathrm{cm}}^{\mathrm{-}1}$. Optical-phonon coupling both to two and to three phonons is necessary to explain the Raman linewidths measured here at the melting temperature and those measured elsewhere at lower temperatures. Coupling to two phonons is important in determining anharmonic corrections to the Raman energy shift, while coupling to three phonons of lower energy is relatively less important. Polarization analysis of the Raman spectra has been used to differentiate the contributions from partially melted and nonmelted regions.