Effect of viscous flow on ion damage near solid surfaces

Molecular dynamics computer simulations of 10 and 20 keV Au bombardment of Au substrates were performed to elucidate the influence of surfaces on defect production. Nearly all of the damage was due to local melting and viscous flow of hot liquid onto the surface. For the 10 keV event, 554 atoms flowed to the surface, and this led to the formation of a dislocation network that extended ≈ 6 nm below the surface. Only three interstitial atoms and no isolated vacancies or small vacancy clusters were produced. Loop punching and the nature of nonlinear sputtering are also discussed.