Study of optical properties of metallic Au : SiO2 and Ni : SiO2 films

To study the optical properties of the metal-insulator granular films, a se ries of NixSiO2(1-x) and AuxSiO2(1-x) granular films was made with variatio n of x and the annealing process. The complex dielectric function was measu red in the 1.5-4.8 eV photon energy range. New spectral features were found in the dielectric functions. For AuSiO2 samples, the new peak in epsilon(2 ) spectra is seen around 2 eV, especially for x = 0.67. The epsilon(1) spec tra change continuously from positive to negative at the low-photon energy range, resulting in a true epsilon(1) associated with the plasmon occurred at 2.0-2.5 eV and at about 3.6 eV for the Au- and Ni-based films, respectiv ely. Comparing to previous data, the experimental results obtained in this work provide richer information to understand better the optical properties of the metal-granular films that are not well predicated by the theoretica l model. The effect will be useful in the metallic multilayer structure des ign applications. (C) 1999 Elsevier Science B.V. All rights reserved.