700 keV Ni+2 ions induced modification in structural, surface, magneto-optic and optical properties of ZnO thin films

Abstract We investigate the effect of 700 keV Ni +2 ions irradiation at different ion fluences (1 × 10 13 , 1 × 10 14 , 2 × 10 14 , 5 × 10 14  ions/cm 2 ) on the structural, surface, magneto-optic and optical properties of ZnO thin films. The X-ray diffraction (XRD) results show improved crystallinity when ion fluence is increased to 2 × 10 14  ions/cm 2 , while deterioration is observed at the highest ion fluence of 5 × 10 14  ions/cm 2 . Scanning electron micrographs (SEM) show the formation of small grains at ion fluence 1 × 10 13  ions/cm 2 , micro-rods at fluences 1 × 10 14 and 2 × 10 14  ions/cm 2 and ultimate fracturing of thin film surface at ion fluence 5 × 10 14  ions/cm 2 . Faraday rotation measurements are also performed and show a decrease in Verdet constant from 53 to 31 rad/(T-m) when irradiated at 1 × 10 13  ions/cm 2 , increasing up to 45 rad/(T-m) at 2 × 10 14  ions/cm 2 , and then decreasing again to 36 rad/(T-m) at 5 × 10 14  ions/cm 2 . The optical band gap energy of the films is determined using spectroscopic ellipsometry, which shows an increase in optical band gap energy ( E g ) from 3.04 eV to 3.19 eV when the fluence increases to 2 × 10 14  ions/cm 2 and a decrease to 3 eV at fluence 5 × 10 14  ions/cm 2 . We argue that these properties can be explained using ion heating effect of thin films.