Ag-MgF_(2) cermet films with different Ag fractions were prepared by vacuum evaporation. The microstructure of the films was examined by Raman scattering technique. The surface-enhanced Raman spectrum for MgF_(2) molecules in the cermet film strongly suggests the existence of Ag nanoparticles dispersed in MgF_(2) matrix. The intensities of the Raman spectra of Ag-MgF_(2) cermet films increase with Ag fraction. The enhancement of Raman scattering disappears when Ag content reaches wt.20%. The analyses with the transmission electron microscopy showed that Ag-MgF_(2) cermet films are mainly composed of amorphous MgF_(2) matrix with embedded faced-center-cubic Ag nanoparticles. It suggests that the percolation threshold should be around wt.20% of Ag content.
© 2005 Chinese Optics LettersPDF Article