FORMATION AND OPTICAL-PROPERTIES OF INTERMETALLIC NANOCLUSTERS FORMEDBY SEQUENTIAL ION-IMPLANTATION

Recent demonstrations that large third-order non-linear responses can be achieved in metal nanocluster glass composites are of significant i nterest because of their potential for use in all optical switching ne tworks. These composite materials exhibit picosecond switching and rel axation times, thermal and chemical stability, high laser damage thres holds, and low two-photon absorption. Ion implantation has been shown to be a useful fabrication method to form these nanoclusters in silica because of its ability to produce thin films in waveguide configurati ons containing a high volume fraction (>1%) of metal colloids with wel l-defined vertical and horizontal dimensional control. Using sequentia l ion implantation of more than one element, we can modify the composi tion and microstructure of the composites by forming intermetallic met al colloids. In this work, we report on the improved optical response of metallic nanocluster composites formed by sequential implantation o f Cd and Ag and Sb and Ag. Characterization of the samples by transmis sion electron microscopy (TEM) reveals that approximately spherical me tallic colloids are formed for all implanted species during the implan tation process. Selected area diffraction patterns indicate that the c olloids formed are intermetallic in composition. Linear optical absorp tion measurements made at room temperature in air from 900 to 200 nm s how significant changes in both the magnitude and wavelength of the su rface plasmon resonance. The formation of intermetallic nanoclusters r esults in changes in both the linear and non-linear optical properties of the composite material that are not possible with single element c olloids alone. The results are explained in terms of effective medium theory. (C) 1998 Elsevier Science S.A.