ANALYSIS OF THE SUBCASCADE STRUCTURE IN COPPER PRODUCED BY ION IRRADIATIONS

The sub-cascade structure has been investigated by analyzing the SFTs (stacking fault tetrahedra) observed with transmission electron microscopy in thin foil copper. In specimens irradiated by ions of various species and energies at room temperature, grouped SFTs were observed, and the number of grouped SFTs increased with maximum PKA (primary knock-on atom) energy. Considering the PKA energy spectrum, the damage energy, and a SFT formation model corresponding to sub-cascades, the number density of SFTs and the distributions of the number of grouped SFTs were analyzed and consistently explained. The effect of successive cascade formation along the ion trace on apparent sub-cascade image formation was estimated by analyses of the spacing of successive cascades and their occurrence probability.