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

Using molecular dynamics simulations of collision cascades, we examine point defect and defect cluster formation mechanisms in metals and semiconductors. In metals we find that the primary mechanism causing separation of interstitials and vacancies is the pushing of vacancies toward the cascade center during the cooling phase of the cascade. We further describe how the isolation of a part of the liquid formed in the cascade can lead to the formation 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 crystal structure. We also find that close to sharp interfaces of metals with different melting points the `vacancy push' mechanism can lead to most vacancies being pushed to most vacancies being pushed to one of the materials, and an symmetric in the impurity introduction over the interface owing to an inverse Kirckendall effects.