Raman and x-ray scattering from ultrafine semiconductor particles

Abstract

We prepared ultrafine germanium particles by gas-evaporation techniques. The particle composition was studied by Raman and x-ray scattering. We take an analytical model to explain the Raman profile: the particle is composed of a single-crystalline core and a coating amorphous shell. In this single-crystalline part, the phonon mode is completely localized, and as a result the red shift and the broadening of the Raman signal are induced. We introduce a localization factor to describe the size effect. According to this model we determined the mean diameter of a crystalline particle. The result is compared with that from x-ray diffraction. Our results indicate that the coating amorphous shell thickness is nearly constant, although the crystalline particle size varies by the evaporation-gas pressure. Furthermore, we found that the Raman profile changes by the wavelength of the exciting laser.