Defect-Stimulated Amorphous Track Formation in SrTiO ₃ and KTaO ₃ – Application of Analytical Thermal Spike Model

Abstract Oxide perovskites exhibit fascinating properties that identify them as key materials for the next generation of multifunctional devices; however, their response to irradiation is complicated. In this work, pre-existing defects/disorder, introduced by ion irradiation, stimulate amorphous track formation at 300 K in single crystal SrTiO 3 and KTaO 3 irradiated with high-energy ions that have electronic stopping power, S e , above a threshold. The track cross-sections increase with S e and level of pre-existing disorder, and the threshold in electronic stopping power, S e th , for track formation decreases with increasing disorder. In both pristine SrTiO 3 and KTaO 3 , temperatures exceeding the normal melt temperature are required to form stable amorphous tracks to offset the significant rate of radial recrystallization during quenching. Application of the analytical thermal spike model to the ion track formation behavior suggests that increasing the concentration of pre-existing defects causes an increase in efficiency for converting S e to thermal energy (electron-phonon coupling) and a decrease in effective melt-quench temperature, which are confirmed by molecular dynamics simulations. This behavior is consistent with the high-level of strain and stored energy with increasing defect concentration that decreases the energy required to melt along the ion trajectory.