Ion-irradiation-induced amorphization of Cu nanoparticles embedded in SiO 2

Abstract

Elemental Cu nanoparticles embedded in SiO2 were irradiated with 5 MeV Sn3+. The nanoparticle structure was studied as a function of Sn3+ 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 (1× 1013 to 1× 1014 ions cm2), 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 1× 1014 ions cm2 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 (1× 1015 to 1× 1016 ions cm2), the nanoparticles were dissolved in the matrix with a Cu coordination similar to that of Cu2 O.