Collision cascades in silicon

Abstract

Individual damaged regions formed in silicon during low fluence (10 11–10 12 ions cm −2) ion bombardments (∼30–200 amu ions of 15–100 keV energy) were observed using transmission electron microscopy. Both monatomic and diatomic ions were used in order to investigate the role of average deposited energy density θ υ in determining the characteristics of the damaged regions. The efficiency of creating a visible damaged region was <0.1 for θ υ<0.1 eV/atom , but increased to 0.7–1.0 for θ υ > 0.4 eV/atom . The fraction of the theoretical collision cascade volume occupied by the damaged regions increased as θ υ increased. During annealing, the number density and the size of the damaged regions decreased but there was no indication of any change in the basic nature of the damaged regions. The damage produced by a diatomic ion was more resistive to annealing than that produced by the corresponding monatomic ion of the same velocity.