Effect of binding energy and mass in cluster-induced sputtering of van-der-Waals bonded systems

We perform a model study of cluster-induced sputtering. By using van-der-Waals bonded systems with Lennard-Jones interaction, we obtain an overview of the influence of the effects of binding energy and mass on the sputtering behavior. We work in the so-called linear regime where the sputter yield is proportional to the total energy of the incident cluster. By varying the cohesive energies U-p and U-t of the cluster projectile and the target, we find that the sputter yield is inversely proportional to U-t and rather independent of U-p. Varying the mass of the projectile atoms, M-p, with respect to that of the target atoms, M-t, gives maximum sputter yields when the projectile atom mass is in the range 0.25M(t) less than or equal to M-p less than or equal to M-t. Furthermore, we study preferential sputter effects in heterogeneous systems. These consist of a random stoichiometric mixture containing equal concentrations of two species. We find that the more weakly bound species is preferentially sputtered. The preferentiality is roughly inversely proportional to the cohesive energy of the pertinent species. We also identify a mass effect on sputtering such that the lighter species is preferentially ejected. (C) 2004 Elsevier B.V. All rights reserved.