MeV–GeV ion induced dislocation loops in LiF crystals

Formation of prismatic dislocation loops and evolution of dislocation structure in LiF crystals irradiated with swift 238U and 36S ions of specific energy 11MeV/u at fluences up to 1013ionscm−2 has been investigated using chemical etching and AFM. It has been shown that prismatic dislocations are formed in the stage of track overlapping above threshold fluences Φ≈109Ucm−2 and Φ≈1010Scm−2. The diameter of dislocation loops reaches 600–1000nm for 238U ions and 200nm for 36S ions. The dislocations created by 238U ions are arranged in rows along the direction of ion beam, whereas 36S ions create freely distributed dislocation loops each of them being oriented along the ion beam. The role of dislocations in ion-induced nanostructuring and hardening is discussed.