Effect of 500 keV Ar2+ ion irradiation on structural and magnetic properties of TiO2 thin films annealed at 900 °C

Abstract

Present study investigates the structural and magnetic properties of TiO2 thin films prepared by electron beam evaporation technique, annealed at 900 °C and irradiated with 500 keV Ar2+ ions. The films before irradiation exhibit anatase phase. Irradiation leads to diffused XRD peaks indicating amorphisation of the anatase phase at the fluence of 1 × 1014 ions/cm2. Increasing the fluence to 5 × 1016 ions/cm2 leads to evolution of brookite phase out of the amorphous TiO2. In addition, an impurity phase, Ti4O7 is observed in pristine as well as in irradiated films, which show radiation resistant behavior to 500 keV Ar2+ ion irradiation upto the highest fluence 5 × 1016 ions/cm2. Anatase to brookite phase transformation followed by an intermediate amorphous phase occurs without showing either grain growth or change in film thickness as evidenced from Atomic Force Microscopy (AFM) and Rutherford’s Back Scattering (RBS) measurements, respectively. Further, both pristine and irradiated films exhibit ferromagnetic behavior at room temperature (RT) irrespective of their phase and crystallinity. The difference in magnetization observed in pristine and film irradiated at ion fluence 5 × 1016 ions/cm2 is ascribed to the difference in oxygen vacancies.