Sputtering of Al nanoclusters by 1-13Â keV monatomic or polyatomic ions studied by Molecular Dynamics simulations

Molecular Dynamics (MD) simulations were employed to study sputtering of freestanding and supported spherical Al nanoclusters with 2-10 nm diameters under bombardment by Al1 and Al13 projectiles with energies of 1-13 keV at normal and oblique incidence. Both monatomic and clustered yields of secondary emission are found to be larger than those for (1 1 1) flat surface of the bulk Al (at equal irradiation conditions). In some events, target nanocluster receives a backward momentum and therefore its major part (more than 1/2 of the mass) is ejected due to produced secondary emission mainly towards the substrate direction. This “recoil effect” is found more pronounced under the impact of cluster projectiles and its probability decreases with increase of the target cluster size. A restricted number of MD simulations were performed to verify whether this “recoil effect” is strong enough to desorb a 4 nm Al nanocluster off an Al (1 1 1) substrate. Desorption was observed under oblique Al13 impact within the impact parameter range of 0.6-0.9.