Ion-beam-induced enhanced diffusion from gold thin films in silicon

We report enhanced diffusion of gold atoms from gold films of various thicknesses (that are deposited on Si) due to 1.5 MeV Au2+ ion impacts under high flux conditions. The maximum depths of mass transport have been found to be 95, 160 and 13 nm for the cases of 5.3, 10.9 and 27.5 nm thick gold films, respectively, at a fluence of 1 × 1014 ions cm−2. Interestingly, at a higher fluence of 1 × 1015 ions cm−2, gold atoms from the 27.5 thick films are transported to a maximum depth of 265 nm in the substrate. The enhanced diffusion for various film thicknesses is consistent with the recoil profiles of Au atoms into Si, which are obtained using Monte Carlo simulations (TRIM). These results have been explained on the basis of the ion-beam-induced flux-dependent amorphous nature of the substrate, and transient beam-induced temperature effects. This work also confirms the absence of ion-induced spike confinement effects that might arise from the morphological nature of the isolated nanostructures.