Amorphous tracks induced by energetic ions in strongly anisotropic solids with layered structures

Common features of ion-induced tracks in layered structures are analysed in Y?Ba?Cu?O, Bi?Sr?Ca?Cu?O and in semiconducting GeS and MoS ₂. In all crystals, the conduction is poor along the normal layer. The anisotropic electron properties lead to the formation of an ion-induced broad and a narrow thermal spike in these solids. The contribution of the two spikes to the formation of tracks can be separated in GeS. When the gap energy is low or zero (Y?Ba?Cu?O, Bi?Sr?Ca?Cu?O, MoS ₂), only the narrow spike controls the track formation, and the localization of the energy deposition is the same as in insulators. However, the fraction of the deposited energy transferred to the narrow spike is only about one-third of that in insulators. The anisotropic features of tracks show the effect of the energy bands. Good quantitative agreement is found between the experimental data and the predictions of the author’s thermal spike model.