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

• 700 keV ion irradiation on ZnO thin films was done at different ion fluence.
• XRD results showed improved crystallinity.
• At lower fluence the microparticles were observed whereas ZnO micro rods were observed at higher fluences.
• The Verdet constant and optical band gap energy of ZnO thin films are also well modified.

We investigate the effect of 700 keV Ni+2 ions irradiation at different ion fluences (1 × 1013, 1 × 1014, 2 × 1014, 5 × 1014 ions/cm2) 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 × 1014 ions/cm2, while deterioration is observed at the highest ion fluence of 5 × 1014 ions/cm2. Scanning electron micrographs (SEM) show the formation of small grains at ion fluence 1 × 1013 ions/cm2, micro-rods at fluences 1 × 1014 and 2 × 1014 ions/cm2 and ultimate fracturing of thin film surface at ion fluence 5 × 1014 ions/cm2. Faraday rotation measurements are also performed and show a decrease in Verdet constant from 53 to 31 rad/(T-m) when irradiated at 1 × 1013 ions/cm2, increasing up to 45 rad/(T-m) at 2 × 1014 ions/cm2, and then decreasing again to 36 rad/(T-m) at 5 × 1014 ions/cm2. The optical band gap energy of the films is determined using spectroscopic ellipsometry, which shows an increase in optical band gap energy (Eg) from 3.04 eV to 3.19 eV when the fluence increases to 2 × 1014 ions/cm2 and a decrease to 3 eV at fluence 5 × 1014 ions/cm2. We argue that these properties can be explained using ion heating effect of thin films.