Optical applications of ion beam irradiation

Layers of various metals (M) buried in Si, SiO2 or Al2O3 were irradiated with various fluences of heavy MeV ions in order to obtain either silicides or nanometric particles that are expected to exhibit interesting optical properties. The mixing of noble metals, Fe and Er with these matrices proceeds either via isotropic di!usion in the metal layer or the growth of compound particles by planar di!usion or a dual mechanism involving recoil implantation and radiation-enhanced di!usion ofMatoms in the matrix. Noble metals form clusters in the oxides directly by lateral segregation and by reprecipitation after diffusing over some distance. Both types of clusters contribute to the absorption resonance of the metal plasmon in the visible part of the spectrum, so that the absorption intensity is not a simple function of the mixing yield. Irradiation of co-sputtered SiO 2 : M layers with a low ion fluence induces more homogeneous precipitation and provides these layers with as interesting optical properties as those obtained by mixing.