Phonon States in Sic Small Particles

Abstract

AbstractSize dependence of optical phonon frequencies and that of phonon dampings of SiC small particles have been studied by analysing their Raman data. The particle size ranges from 30 nm to 1000 nm. Decrease in the TO-phonon frequency as well as the LT-splitting (the splitting between the LO- and TO-phonon) with decrease in the particle size are much larger than that expected from the spatial correlation model or that from the phonon confinement model. The phonon damping for the small particle consists of the usual temperature-dependent term and an excess damping term, which is independent of temperature. These results suggest that the scattering of the phonon at the particle surface plays a major role in determining the phonon states of the small particle. Our experimental data suggest that the surface phonon-polariton mode at the interface between the crystallites plays a minor role in the Raman spectrum of particles consisting of a number of crystallites.