The optical properties of gold nanocluster composites in silica formed by ion beam assisted deposition

Describes the linear and nonlinear optical (NLO) properties of thin films of gold nanoclusters in silica matrices, produced by a technique called ion beam assisted deposition (IBAD). IBAD has achieved a significant amount of application in the optical thin-film industry due mainly to the fact that IBAD films are denser than evaporated or sputtered films. We have used the technique in recent years to produce metal and semiconductor nanoclusters embedded in dielectric matrices. Metal nanocluster thin film consisting of clusters 5-30 nm in size embedded in an active metal oxide matrix were deposited by co-evaporation of two metals, one more highly reactive toward oxygen than the other, with O₂⁺ ion bombardment. We have also produced nanoclusters in dielectrics by co-evaporation of a metal and a dielectric. Here the ion beam (e.g. argon) is used to control the microstructure of the nanoclusters and to densify the films. Values of χ⁽³⁾/α (where α is the absorption coefficient) for the IBAD films were as good as or even superior to those reported for ion implanted film. The advantages of the IBAD method for fabricating films with NLO properties include the ability to deposit films with greater active region thicknesses, higher nanocluster densities and more uniformly sized nanoclusters