Collision cascades in metals and semiconductors: defect creation and interface behavior

Using molecular dynamics simulations of collision cascades, we examine poin t defect and defect cluster formation mechanisms in metals and semiconducto rs. In metals we find that the primary mechanism causing separation of inte rstitials and vacancies is the pushing of vacancies toward the cascade cent er during the cooling phase of the cascade. We further describe how the iso lation of a part of the liquid formed in the cascade can lead to the format ion of interstitial clusters in metals. By comparing ballistically similar pairs of metals and semiconductors like Al and Si and Cu and Ge, we deduce how the cascade behavior depends on the nature of interatomic bonding and c rystal structure. We also find that close to sharp interfaces of metals wit h different melting points the 'vacancy push' mechanism can lead to most va cancies being pushed to one of the materials, and an asymmetry in the impur ity introduction over the interface owing to an inverse Kirkendall effect. (C) 2000 Elsevier Science B.V. All rights reserved.