Computer simulation of multimers sputtered from copper.

Abstract

The formation of clusters of sputtered atoms, called multimers, has been investigated in a digital computer simulation of single crystal copper bombarded with argon ions. Five formation mechanisms for sputtered dimers and four formation mechanisms for sputtered trimers were identified and analyzed in detail. The mechanisms did not reveal a single case in which a multimer was formed by the motions of a single ion or atom. Multimers were found to be caused by various interactions of the projectile ion with atoms in the first four layers of the crystal. Nearest neighbor atoms in the crystal rarely formed dimers or trimers. Next nearest neighbor clustering was much more common. Members of a multimer usually were not emitted simultaneously. Often four or five collisions by the ion or its primary knock-on atoms would intervene between the emission events, but the relatively slow speed of the emitted atoms still allowed cluster formation.