Features of collision cascades in silicon as determined by transmission electron microscopy

Abstract

Studies have been performed on individual damaged regions in Si using high resolution transmission electron microscopy techniques. The damaged regions were produced during implantation at 40–50 K with monatomic and diatomic ions of As, Sb and Bi (10–120 keV energy) to fluences of 1 × 10 11–6 × 10 11 ions cm −2. All of the damaged regions investigated gave rise to contrast which was principally of the structure factor type and these regions are best described as being ‘amorphous’. The fraction of the theoretical collision cascade volume occupied by the damaged regions increased steadily as the average deposited energy density θ ν increased and at θ ν⪆1 eV/atom the average diameter of the damaged regions was equal to or greater than twice the mean transverse straggling of the deposited energy distribution. At low energy densities θ ν⪅0.1 eV/atom , multiple damaged regions were formed quite frequently within a single collision cascade i.e. sub-cascade structure had developed. The annealing behaviour of the induced damage was investigated using monatomic and diatomic Bi implants with θ ν ranging from 0.09 to 2.7 eV/atom. The damage produced by a diatomic ion was always more resistive to annealing than that produced by the monatomic ion of the same velocity. However, the temperature regimes in which the annealing occurred show no simple dependence upon θ ν .