Structural and Raman spectra studies of supported LiF clusters

Electron microscope and Raman scattering spectra are used to study the structures and properties of supported LiF clusters prepared by gas-evaporation technique. The experiments demonstrate that large-size LiF clusters have fee structure and cubic shape, but have no Raman scattering spectrum. As cluster size decreases, cluster shape deviates from cube and tends to be spherical, fractal structure appears and the size distribution becomes narrow. When clusters size is 10 nm, very conspicuous Raman spectrum is obtained. If clusters size decreases to 5 nm, the fine structure of Raman spectrum is observed. Fine structure in small cluster reflects the dicreteness of the wave vector and the intensity of cluster-substrate interaction.