<title>Heavy-ion induced damage and reduction of dislocation mobility in LiF single crystals</title>

Abstract

Ion-induced reduction of dislocation mobility in LiF crystals irradiated with swift heavy (U) and light (Ni) ions of a specific energy of 11 MeV per nucleon at fluences between 10⁶ and 10¹¹ ions/cm² was studied. The arm length of dislocation rosettes produced by indentation on (100) irradiated surface was measured. It has been found that in the case of heavy ions the threshold fluence (10⁶ ions/cm²) for impeding of dislocation arms is about 3 orders of magnitude lower than that for light ions. The results indicate that ion-induced defect aggregates play the dominating role in the impeding of dislocations. Heavy ions, which produce defect aggregates in the track core, cause also a stronger effect of dislocation impeding and surface hardening. In the case of light ions, the reduction of dislocation mobility is observed at higher fluences (>10⁹ ions/cm²) where the defect aggregates are created in the halo by neighbour track overlapping. The results show that fast heavy ions are suitable for nanoscale structuring and surface modification of materials.