Revealing ionization-induced dynamic recovery in ion-irradiated SrTiO₃

The lack of fundamental understanding on the coupled effects of energy deposition to electrons and atomic nuclei on defect processes and irradiation response poses a significant roadblock for the design and control of material properties. In this work, SrTiO₃ has been irradiated with various ion species over a wide range of ion fluences at room temperature with a goal to deposit different amounts of energy to target electrons and atomic nuclei by varying the ratio of electronic to nuclear energy loss. The results unambiguously show a dramatic difference in behavior of SrTiO₃ irradiated with light ions (Ne, O) compared to heavy ions (Ar). While the damage accumulation and amorphization under Ar ion irradiation are consistent with previous observations and existing models, the damage accumulation under Ne irradiation reveals a quasi-saturation state at a fractional disorder of 0.54 at the damage peak for an ion fluence corresponding to a dose of 0.5 dpa; this is followed by further increases in disorder with increasing ion fluence. In the case of O ion irradiation, the damage accumulation at the damage peak closely follows that for Ne ion irradiation up to a fluence corresponding to a dose of 0.5 dpa, where a quasi-saturation of fractional disorder level occurs at about 0.48; however, in this case, the disorder at the damage peak decreases slightly with further increases in fluence. This behavior is associated with changes in kinetics due to irradiation-enhanced diffusional processes that are dependent on electronic energy loss and the ratio of electronic to nuclear energy dissipation. These findings are critical for advancing the fundamental understanding of ion-solid interactions and for a large number of applications in oxide electronics where SrTiO₃ is a foundational material.