Study of optical properties of metallic Au : SiO 2 and Ni : SiO 2 films

Abstract

To study the optical properties of the metal–insulator granular films, a series of Ni x SiO 2(1 −x) and Au x SiO 2(1 −x) granular films was made with variation of x and the annealing process. The complex dielectric function was measured in the 1.5–4.8 eV photon energy range. New spectral features were found in the dielectric functions. For AuSiO 2 samples, the new peak in ε 2 spectra is seen around 2 eV, especially for x=0.67. The ε 1 spectra change continuously from positive to negative at the low–photon energy range, resulting in a true ε 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, respectively. 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 theoretical model. The effect will be useful in the metallic multilayer structure design applications.