Bulk, overlap and surface effects of swift heavy ions in CeO2

Formation of tracks of swift heavy ions decelerating in the electronic stopping regime in CeO₂ was studied, combining the Monte Carlo code TREKIS with molecular dynamics. We show that strong lattice disordering (melting) followed by structure recovery form finally a damaged ion track consisting of a discontinuous crystalline region in CeO₂. Normal ion impacts result in appearance of spherical crystalline hillocks on CeO₂ surface. The solid-vacuum interface strongly suppresses the recrystallization of the near-surface layers, forming conically shaped tracks with several tens of nanometers lengths. Grazing ion irradiation induces intensive material expulsion from the surface forming finally grooves surrounded by nanohillocks. The processes of surface nanostructures formation is similar to those observed previously in CaF₂ which has the similar crystalline structure, however requires much longer recrystallization time. Recent experimental data confirm the simulation results.