One Phonon Raman Scattering of CdS Microcrystals Embedded in a Germanium Dioxide Glass Matrix

Abstract

Raman scattering spectra of LO phonon modes in CdS microcrystals having various sizes in a germanium dioxide glass matrix are measured. The bandwidth of the LO phonon broadens with decreasing the microcrystal size. The size dependence of the bandwidth agrees with the calculated results based on the phonon confinement theory. This result shows that this size dependence originates from the relaxation of the q -vector selection rule. However, for the microcrystal sizes smaller than d =5.0 nm, the higher-frequency shift of the LO phonon peak with decreasing the microcrystal size were observed in contrast to the prediction by the phonon confinement theory. The origin of this shift might be due to the defects contained in the CdS microcrystals.