Radiation damage induced by swift heavy ions in TiO2 sol–gel films nanocrystallines

Abstract

TiO2 films prepared by sol–gel were irradiated with 25.8MeV Cu and 90MeV Xe ions at room temperature under normal incidence. The irradiation with Cu and Xe ions were performed respectively at iThemba labs, South Africa and GANIL, Caen, France. The properties of radiation defects induced in TiO2 nanostructures were investigated using grazing angle X-ray diffraction (GAXRD), atomic force microscopy (AFM) and UV–visible spectrophotometry. From GAXRD analysis, it is found that anatase (101) peak intensity decrease with increasing the fluence and disappear completely above a threshold ion fluence of 5×1012ion/cm2. This indicates that the crystallinity of the TiO2 film is destroyed upon irradiation due to the amorphous track formation. The track radius estimated from the Poisson’s law is about 2 and 4nm after irradiation with 25.8MeV Cu and 90MeV Xe ions, respectively. According to the AFM analysis, the elaborated TiO2 films are composed of particles with a triangular shape of a size in the range of 200–500nm. It is found that the particle size increases after irradiation with both Cu and Xe ions. In addition, the root-mean-square (RMS) surface roughness for 780nm×780nm area scans decreases exponentially with increasing fluence up to 1013ions/cm2 in the case of Xe irradiation, but increases drastically above 2.68×1011ions/cm2 in the case of Cu ion irradiation and reaches a mean value of ∼3nm. The absorption measurements reveal that the optical band gap is not affected by both Xe and Cu ions irradiation.