RAMAN-SCATTERING FROM SURFACE PHONONS IN FINE ZN PARTICLES COATED WITH ZNO

Using a gas-evaporation technique with an induction-heating method, Zn fine particles were prepared. Transmission electron microscopic obser vations showed that Zn with spherical form are about 80 nm in diameter . X-ray diffraction revealed that the particle is composed of a Zn cor e and a ZnO coating. Raman scattering from the Zn fine spherical parti cles coated with ZnO of variable thickness was measured, and a broad p eak was observed. The Raman peak shifts to the lower-frequency side wi th the increase of oxide thickness. To explain the experimental result s, the frequencies of the optical-surface phonons of a metallic sphere with a dielectric coating were derived. In particular, the dependence of the frequencies on the thickness of the coating was investigated. From a comparison of experimental results with theoretical analysis, i t was concluded that the broad Raman peak comes from the surface-phono n scattering.