Effects of intermediate energy heavy-ion irradiation on the microstructure of rutile TiO₂ single crystal

This study reports the microstructure evolution of single crystal rutile TiO₂ under 3 MeV Nb⁺ ion irradiation, with the irradiating ions incident on the {100} plane. A complex, multi-layered microstructure evolution is observed with 4 distinct regions: (i) short-range disorder in the first 60 nm below the specimen surface, (ii) dislocation loops oriented parallel to the incident ion beam direction, located along the increasing slope of the irradiation damage profile at ~60-650 nm from the surface, (iii) loops oriented perpendicular to the incident ion beam direction, at depths encompassing the ion implantation and irradiation damage peaks ~650-1250 nm, and (iv) a high density of nano-scale atomic rearrangements with long-range order, located at depths ~1250-1750 nm. These results present evidence that multiple defect mechanisms occur during irradiation including ion channeling, nuclear stopping, and electronic stopping interactions as a function of depth and disorder accumulation.