Effect of 100 MeV Au irradiation on embedded Au nanoclusters in silica glass

Embedded Au nanoclusters (NCs) in silica glass were formed by ion beam synthesis using 32 keV Au− implantation to a fluence of 4 × 1016 ions cm−2. Subsequently the NCs were irradiated with swift heavy ions in the form of 100 MeV Au8+ at ∼100 K in the fluence range of 5 × 1012–1 × 1014 ions cm−2. Samples were analyzed using Rutherford backscattering spectrometry, transmission electron microscopy and optical absorption spectroscopy. At lower irradiation fluence the high energy heavy ion irradiation has been found to result in a loss in Au due to an outward movement of the NCs together with a growth in size. At the highest irradiation fluence, almost 80% Au was lost, with only few large NCs seen which had moved to the surface. These were found to be of a deformed non-spherical shape. The amount of Au lost has been found to linearly increase with irradiation fluence indicating the movement of Au to be not dominated by diffusion. Results indicate the importance of nuclear energy loss in sputtering at very high energies.