Sputtering of a Au surface covered with large spherical clusters

Abstract

Using molecular-dynamics simulation, we study the effect of 100 keV Au atom bombardment of a Au (111) surface, which is covered with large spherical Au clusters (radius R = 40 Å). Only a limited number of atom impact locations could be studied, all of which were focused within 2 Å of the center of the cluster. Depending on the exact atom impact point on the cluster surface, strong fluctuations in the sputter yield are found; in the most dramatic cases, the cluster completely disintegrates. The 1/E2-energy distribution of sputtered atoms is in agreement with a collisional emission mechanism. Large fragment clusters are emitted during sputtering.Further, in order to study the possibility of intact cluster desorption, we performed a model study, in which a hemispherical part of the substrate immediately below the cluster is heated up to high temperatures, corresponding to an initial energy E0 per atom. Such a scenario may be relevant for fast heavy-ion bombardment, where the substrate is heated by strong electronic stopping. Intact desorption of the cluster is observed above a threshold of E0 ≅ 3 eV/atom. Then the kinetic translational energy of the desorbed cluster is more than around 20% of its internal energy.