Fullerene genesis by ion beams III. On the absence of latent tracks in GeV ion irradiated graphite

Irradiation of natural graphite with ∼ 1 GeV lead and uranium ions initiates a phase change to fullerene (C₆₀) along the particle trajectories. High resolution transmission electron microscopy (Dunlop et al. [1]) reveals no tracks in the bulk in either kinematic or diffraction contrast. Small amoeboid-like surface patches are formed however, random in distribution and proportional in number, but not equivalent to the total ion fluence. The evidence suggests that molecules of C₆₀ and other clusters are ejected from the entry and exit surfaces by electronic sputtering and are then deposited. A mechanism referred to as particle activated prompt anneal (or PAPA) is proposed to explain the absence of latent tracks in the bulk. A reverse cooling and annealing wave permits recovery by epitaxy of the disorder and phase changes induced by the primary heat wave. Radiation enhanced recovery processes may also play a role. PAPA can additionally explain the absence of induced fission fragment tracks in graphite, diamond, silicon and germanium.