Laser annealing of metal-dielectric nanocomposites formed by ion implantation

Abstract

Metal-dielectric composites have been fabricated by ion synthesis of silver nanoparticles in soda-lime silicate glass. Ion implantation has been performed with Ag + ions at 60keV to a dose of 4 10 16 ionscm -2 . The glass was annealed using pulses of a high-power KrF excimer laser (248nm) in an ambient atmosphere. This employed a single (25ns) pulse fluence of 0.25Jcm -2 for implanted samples. From 1 to 250 pulses with the same energy densities and at a frequency of 1Hz were accumulated in the same area on the glass surface. The formation and modification of metal nanoparticles were assessed via optical reflectance, combined with Rutherford back-scattering analysis. Generally, changes induced by laser pulses suggest there are both reductions in the nanoparticles and some longer-range diffusion of metal atoms into the glass. However, before the total dissolution of metal nanoparticles occurs, increases in the substrate temperature during many-pulse treatments initiate the regrowth of new metal nanoparticles, which leads to a rise in the reflectance. These results are discussed on the basis of surface substrate melting.