COLLISION CASCADES AND SPUTTERING INDUCED BY LARGER CLUSTER IONS

Recent experimental work on larger cluster impact on solid surfaces suggests large deviations from the standard case of additive sputter yields both in the nuclear and electronic stopping regime. The paper concentrates on elastic collision cascades. In addition to very pronounced spike effects, two phenomena are pointed out that are specific to cluster bombardment. Multiple hits of cluster atoms on one and the same target atom may result in recoil atoms that move faster than the maximum recoil speed for monomer bombardment at the same projectile speed. This effect is important when the atomic mass of a beam atom is less than that of a target atom, M1 ≪ M2. In the opposite case, M1 ≫ M2, collisions between beam particles may accelerate some beam particles and slow down others. Some consequences are mentioned. Remarks on the nuclear stopping power of larger clusters and on electronic sputtering by cluster bombardment conclude the paper