Molarity dependence of solution on structural and hydrophobic properties of ZnO nanostructures

The impact of the molarity solution on this property of elaborated ZnO thin films coating on a metallic aluminum substrate are the aim of this present work. ZnO is the chosen material to be deposited in this work; it is one of the most used materials in the development of hydrophobic surfaces due to its interesting physical and structural properties. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (FEG-SEM) equipped with energy dispersive X-ray analysis (EDX) and a profilometer. The wettability properties of the synthesized films were analyzed by measuring the contact angle between the surface of studied films and a deposited water drop (WCA). XRD analysis and Raman spectroscopy show that ZnO is well synthesized by thermal oxidation in this present work, where the crystallization of the deposited layer increases with increasing solution molarity. The calculated crystallite sizes are in the nanometric scale and reach their maximum value for the prepared solution of 0.3 M with an average crystallites size of 32 nm. The obtained results show that the surface morphology strongly depends on solution molarity and has an effect on the hydrophobic properties of the elaborated ZnO thin films. The elaborated sample with solution of 0.2 M shows compact granular attached to each other with an average size of 200 nm. Measured surface roughness ranges from 7.653 µm to 0.526 µm. The shape and surface roughness of the prepared thin layers had an effect on the surface hydrophobicity. The largest measured contact angle of 135.72 °, was achieved with a solution molarity of 0.2 M with the greatest roughness indicate the best hydrophobicity of this sample.