“…The ion-induced surface hillocks are observed more often in two material categories, namely ionic fluoride crystals such as LiF, CaF 2 , BaF 2 , and LaF 3 [3][4][5][6], as well as oxide materials like TiO 2 , Y 3 Fe 5 O 12 , Al 2 O 3 , SiO 2 , MgO and LiNbO 3 [7][8][9][10][11][12]. The most common scenario for the mechanism, which describes the creation of hillocks by swift heavy ions, is what is termed modified thermal spike model [13,14]. It describes the formation of ion track in two consequent steps by the initial ion induced strong electronic excitations, in a time scale of 10 −18 to 10 −15 s, and the subsequent coupling between the thermalized emitted electrons and the phonons.…”