Excimer laser annealing of glasses containing implanted metal nanoparticles

Silver and copper nanoparticles have been synthesized by ion implantation in silica and soda-lime silicate glass at 60 keV to a dose of 4 x 10(16) ion/cm(2) and at 50 keV to a dose of 8 x 10(16) ion/cm(2), respectively. The glasses were annealed using pulses of a high-power KrF excimer laser (248 nm) in ambient atmosphere. This employed a single (25 ns) pulse fluence of 0.25 J/cm(2) for Ag-implanted samples or of 0.21 J/cm(2) for Cu-implanted ones. Several pulses from 1 to 250 of the same energy density at a frequency of 1 Hz were accumulated in the same area on the surface. The formation and modification of metal nanoparticle was assessed via optical reflectance, combined with Rutherford backscattering analysis. Generally, changes induced by laser pulses suggest there are both reductions of the nanoparticles and some longer-range diffusion of metal atoms into the glass. However, before the total dissolution of metal nanoparticles is accrued, the substrate temperature, increasing during many-pulse treatments, initiates the regrowth of new metal nanoparticles that leads to a rise of the reflectance. These results are discussed on the basis of a surface substrate melting. This work is part of an attempt to gain control over the size and depth distribution of such metal nanoparticles. (C) 2000 Published by Elsevier Science B.V. All rights reserved.