Modification of LiF structure by irradiation with swift heavy ions under oblique incidence

The structural modifications of LiF irradiated with swift heavy ions under oblique angles have been investigated using AFM, SEM, chemical etching, nanoindentation and optical absorption spectroscopy. LiF crystals were irradiated under incidence angles of 30 and 70 degrees with 2.2 GeV Au (fluence 57×l0¹¹ ions-cm²) and 150 MeV Kr ions (fluence 10¹²–10¹⁴ ions·cm⁻²). Structural study on sample cross-sections shows that two damage regions – (1) nanostructured zone and (2) dislocation – rich zone, which are typical for irradiations at normal incidence, appear also in samples irradiated under oblique angles. However in the latter case a more complex structure is formed that leads to stronger ion-induced hardening