Sensitivity of Anatase and Rutile Phases of TiO 2 to ion irradiation: Examination of the applicability of Coulomb Explosion and Thermal Spike Models

International audienceSensitivity of the anatase and rutile phases of titanium dioxide to Swift Heavy Ion (SHI) irradiation wasexperimentally probed and compared with the predictions of the Coulomb explosion, analytical andinelastic thermal spike models of ion-matter interaction. Conforming to the predictions of all thesemodels, our study indicated higher sensitivity of anatase to these ions than the rutile phase. A detailedexamination however revealed that Coulomb explosion model cannot explain either the nature ofvariation of the interaction cross section of SHI with the energy deposited by these ions, Se to the targetelectrons, or the relative values of the threshold electronic energy loss, Seth of anatase and rutile. Theanalytical thermal spike (a-TS) model, using the available physicochemical data for this oxide, predictedthat tracks cannot form either in anatase or in rutile by 297 MeV and 511 MeV Ni ions, while inelasticthermal spike (i-TS) model predicted formation of ion tracks by 297 MeV Ni ions and their absencewith 511 MeV Ni ions in both anatase and rutile. Our observation agreed with the predictions of i-TSmodel albeit with a difference in the radius of the tracks. In addition, we observed halo of defect riddencrystalline region of much larger radius around the ion track. Interestingly, the radius of the halo scaleswith the velocity of the ions, which is opposite to the conventionally observed velocity effect