TRIM [4, 5] calculations show simulated collision cascades of 5 kV and 30 kV gallium ions in amorphous silicon (modeled with 2 eV lattice binding energy, 4.7 eV surface binding energy, and 15 eV displacement energy). Plotted are 500 gallium ion trajectories in red, all entering normal to the surface at a single point, each as a single event and then superimposed. The green trajectories are of misplaced silicon atoms, which are plotted on top of the red ones in order to visualize the full volume where changes do happen due to the ion impact. Without taking into account actual gallium ion beam diameters, the simulated interaction volume is roughly 15 nm diameter wide and 15 nm deep for 5 kV and 40 nm diameter wide and 50 nm deep for 30 kV gallium ions. The average distribution of deposited energy per ion is shown in (g) and (h).
