Cluster beam steering onto silicon surfaces studied by molecular dynamics

The purpose of this study is to investigate the effects of the impact conditions on cluster deposition in silicon and is motivated by recent results obtained using a variable incidence angle during deposition of metallic clusters and atoms. Therefore deposition of silicon clusters with a kinetic energy in the range from 0.5 to 10 eV/atom directed at normal and grazing incidence onto crystalline silicon has been studied using a molecular dynamics simulation method. The influence of other relevant parameters, such as the interatomic forces and the cluster size and shape, has also been investigated. This study shows that the physics of deposition is almost entirely dictated by the nature of the interatomic forces. When using potentials with the four-fold coordination typical of bulk a clear dependence on the size N is observed and the spreading index decreases with the increase of N for all incidence conditions. The cluster binding strength is perceptibly increased when using a potential accounting for the coordination typical of clusters. In this case is reduced of almost one order of magnitude with respect to the values calculated with the bulk potentials and its value is independent of N. Also compact clusters, obtained from a quantum mechanical minimization of the total energy, show an enhanced resilience against fragmentation.