Structural and Optical Characteristics of Zinc Oxide Nanostructures Deposited by Reactive Magnetron Sputtering: Role of Gas Mixing Ratio

Abstract

The reactive magnetron sputtering was employed to synthesize zinc oxide (ZnO) nanostructures at different Ar:O₂ gas mixing ratios. The formation of wurtzite phase of ZnO was confirmed with larger crystallinity at higher O₂ ratios and reduced average crystallite size at the highest Ar ratio. The Zn-O stretching vibration besides O-H bending and stretching modes were revealed, indicating higher hydroxyl adsorption at larger oxygen content. The gas ratio was found strongly influencing topographic morphology of ZnO films where the O₂-rich conditions produced finer and more homogeneous nanostructures, whereas Ar-rich deposition promoted grain formation and surface roughness. The prepared material showed stoichiometric composition with no traces for other elements or impurities as well as showed strong UV absorption (350-360 nm) and high transmittance in the visible range. The values of energy band gap (3.56-3.78 eV) were found to decrease with decreasing O₂ ratio, highlighting the importance of reactive magnetron sputtering of the synthesis highly efficient ZnO nanostructures to satisfy the requirements of many applications including photocatalytic and biomedical applications.