Formation of dislocations and hardening of LiF under high-dose irradiation with 5–21 MeV 12 C ions

The emergence of dislocations and hardening of LiF crystals irradiated to high doses with 12 C ions have been investigated using chemical etching, AFM, nanoindentation, and thermal annealing. At fluences ensuring the overlapping of tracks ( Ф ≥6 × 10 11 ions/cm 2 ), the formation of dislocation-rich structure and ion-induced hardening is observed. High-fluence (10 15 ions/cm 2 ) irradiation with 12 C ions causes accumulation of extended defects and induces hardening comparable to that reached by heavy ions despite of large differences in ion mass, energy, energy loss, and track morphology. The depth profiles of hardness indicate on a notable contribution of elastic collision mechanism (nuclear loss) in the damage production and hardening. The effect manifests at the end part of the ion range and becomes significant at high fluences (≥10 14 ions/cm 2 ).