Raman scattering from CdSe microcrystals embedded in a germanate glass matrix

Abstract

Raman-scattering spectra of LO-phonon modes in CdSe microcrystals of various sizes in a germanate glass matrix are measured. The frequency of the peak shifts towards the lower-frequency side and the bandwidth broadens with decreasing microcrystal size. The size dependences of the peak shift and the broadening of the bandwidth agree with those calculated on the basis of the phonon confinement model. These results show that these size dependences originate from the relaxation of the q-vector selection rule. From the temperature dependence of the Raman-scattering spectra, we find that the bandwidth consists of a temperature-dependent intrinsic width of a zone-center phonon and a temperature-independent additional width due to phonon dispersion. We find that the size dependence of the intrinsic width in a microcrystal shows an increment in the decay rate of the zone-center phonon, and it is in good agreement with predictions of the phonon confinement model.