Emission of Cluster Ions During Surface Sputtering
George G Meskhi
ABSTRACT
Atomic clusters—aggregates of atoms bound by interatomic forces—represent a distinct intermediate state between isolated atoms (or molecules) and bulk solids. Investigating cluster properties provides fundamental insight into the transition from single atoms to the solid state and enables the design of materials with novel chemical and physical functionalities. Clusters can be generated through adiabatic gas expansion, laser evaporation, or surface sputtering induced by ions, electrons, or photons. Despite extensive studies, the underlying mechanisms governing cluster emission under ion bombardment, including the formation of positive and negative clusters and their excited states, remain incompletely understood.
In this work, we present a comprehensive experimental study of cluster ion emission from C, NaCl, Mg, Al, Si, S, Ti, and GaAs surfaces under 0.5–50 keV N⁺, O⁺, N₂⁺, O₂⁺, and Ar⁺ bombardment. The dependence of cluster yield on size is analyzed, with particular emphasis on small ("light") clusters (n < 10), which form via collective atomic motion during collision cascades. Localized energy deposition near the surface may lead to correlated emission of neighboring atoms that remain bound as clusters. These findings provide further insight into the mechanisms of cluster formation and the role of projectile type in ion-surface interactions.
