LAUSR

Abstract The effect of 5 MeV Cu ++ ions irradiation on structural and optical properties of Anatase TiO 2 nanoparticles (TiO 2 -NPs) is investigated. For this purpose, TiO 2 -NPs are irradiated with different Cu ++ ions fluences, ranging from 1 × 10 15 to 1 × 10 16  ions/cm 2 at room temperature. XRD results confirm the Ti 3 O 7 phase appear at the dose of 5 × 10 15  ions/cm 2 and peak intensity of Ti 3 O 7 phase gradually increases with an increase of Cu ++ ions irradiation dose. At the dose of 1 × 10 16  ions/cm 2 TiO 2 Anatase phase were transformed to Rutile phase. Same observations are confirmed from Raman spectroscopy. High resolution transmission electron microscopy (HRTEM) reveals that morphology converted into wavy shape and crystal structure detrioted with increase Cu ion irradiation dose to form vacancy loops and interstitial loops. Scanning electron microscopy (SEM) shows that TiO 2 -NPs have been fused to form a cluster of nanoparticles at high Cu ion beam dose, while bandgap of TiO 2 -NPs reduces from 3.19 eV to 2.96 eV as a function of Cu ++ irradiation fluence. These phase transformations and crystal damage are the responsible for optical bandgap reduction. The mechanism for the currently observed phase transformation of TiO 2 and coalescence of TiO 2 -NPs are discussed in term of thermal spikes model.