Investigation on structural, linear, nonlinear and optical limiting properties of sol-gel derived nanocrystalline Mg doped ZnO thin films for optoelectronic applications

Nanostructured thin films of pure as well as Mg-doped Zinc Oxide (MZO) were successfully casted on glass substrates through sol-gel technique. X-ray diffraction patterns display that all deposited films exhibit good crystallinity, hexagonal wurtzite structure and are preferentially grown along (002) plane (i.e. C-axis). Surface morphology, vibrational modes and optical properties were inspected by AFM, FT-Raman and UV–Visible–NIR spectroscopy. AFM Analysis revealed the uniform nanowire growth of MZO films where each nanowire was made up of very fine nanoparticles. The grain size was found to be increased from 16 to 25 nm with increasing the Mg-doping which agreed with the crystallite sizes obtained from the XRD analysis. The linear and nonlinear optical functionals were evaluated from optical data. Further, the deposited films were subjected to Z-scan measurement and studied its different key properties. The values of χ⁽³⁾ is found to be enhanced from 0.27 × 10⁻⁸ to 4.36 × 10⁻⁸ due to Mg doping. The optical limiting threshold of MZO nanostructured films are also studied, and the obtained threshold values are found in the range 1.7 to 7.4 kJ/cm². These low values suggests that the fabricated films can be used as optical limiters to protect sensor devices from high intensity light.