Ultrasonic sol-gel dip coating of multilayer niobium-doped ZnO thin films: Analysis of optical properties

This study investigates the synthesis of multilayer Nb-doped ZnO thin films using an ultrasonic-assisted sol-gel dip-coating technique. The work aims to bridge a gap in the literature by examining the influence of multilayer deposition on optical and structural properties, which has not been extensively reported. The films demonstrate over 95 % transmittance in the visible range and increased absorption in the ultraviolet region. The six-layered thin film exhibited the highest optical performance, attributed to uniform particle size distribution and minimal structural defects. UV-vis spectroscopy revealed an optical bandgap ranging from 3.26 to 3.69 eV, while FESEM analysis indicated an average particle size of 24.8-25.2 nm. EDAX confirmed successful niobium doping, and XRD patterns identified a hexagonal wurtzite crystalline structure with a predominant (002) orientation. These findings highlight the potential of the ultrasonic sol-gel dip-coating method in fabricating high-quality optical thin films.