Hydrophobic Properties of CuO Thin Films Obtained by Sol-Gel Spin Coating Technique-Annealing Temperature Effect

Abstract

The adhesive characteristics of sol-gel copper oxide (CuO) film surfaces at annealing temperatures ranging from 350 to 550°C were examined in this work. Hydrophobic properties of these oxide film surfaces were studied by contact angle measurements. The surface energy was calculated from contact angle data using harmonic mean method. The structural, morphological and chemical analysis of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). The increase in annealing temperature induces a reduction in the hydrophilic properties of the films (adhesive properties). The rise in the hydrophobicity of the CuO surface has been claimed to be explained by a change in interfacial tension. The FTIR spectroscopy analysis revealed that the increase in the annealing temperature eliminates activated neutral species (hydroxyl groups) reacting with the surface of the sample responsible for the wettability. SEM analysis showed that the morphology of the samples is nanostructured containing agglomerates of various forms, a few hundred nanometers in size, randomly dispersed across the surface. The enhanced roughness of the produced film is primarily responsible for the increased hydrophobicity of the films. The XRD data reveal that the films are highly textured and that increasing the annealing temperature induces better layer crystallization and confirms the development of copper oxide CuO.