Optical properties of Au nanocluster embedded dielectric films

Composite films of Au and dielectric material (TiO2 and/or mixed ZnS–SiO2) with a wide range of Au fractions were fabricated through a co-sputtering method utilizing a multi-target sputtering system. The optical absorption spectra of these composite films demonstrated an absorption peak due to surface plasmon resonance of embedded Au nanoclusters. It was found that, depending on the dielectric matrix, Au concentration, and post-deposition annealing, the wavelength of the surface plasmon resonance of nanoclusters shifted by 130 nm: from 550 to 680 nm. The third-order non-linear susceptibility χ(3) of these composite films, which also originates from field enhancement due to the surface plasmon resonance, demonstrated a corresponding variation.