Ion-irradiation-induced amorphization of Cu nanoparticles embedded inSiO2

Abstract

Elemental Cu nanoparticles embedded in SiO{sub 2} were irradiated with 5 MeV Sn{sup 3+}. The nanoparticle structure was studied as a function of Sn{sup 3+} fluence by extended x-ray absorption fine structure spectroscopy, small-angle x-ray scattering, and transmission electron microscopy. Prior to irradiation, Cu nanoparticles exhibited the face-centered-cubic structure. Upon irradiation at intermediate fluences (1x10{sup 13} to 1x10{sup 14} ions/cm{sup 2}), the first nearest neighbor Cu-Cu coordination number decreased, while the Debye-Waller factor, bondlength, and third cumulant of the bondlength distribution increased. In particular, at a fluence of 1x10{sup 14} ions/cm{sup 2} we argue for the presence of an amorphous Cu phase, for which we deduce the structural parameters. Low temperature annealing (insufficient for nanoparticle growth) of the amorphous Cu returned the nanoparticles to the initial preirradiation structure. At significantly higher irradiation fluences (1x10{sup 15} to 1x10{sup 16} ions/cm{sup 2}), the nanoparticles were dissolved in the matrix with a Cu coordination similar to that of Cu{sub 2}O.