Hydrophobic and textured ZnO films deposited by chemical bath deposition: annealing effect

Highly textured ZnO cones have been grown onto glass substrates by chemical bath deposition (CBD) method. They were given heat treatment at 623 K for 2 h in air. The change in structural, optical and electrical properties were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption, electrical resistivity and contact angle measurements. Structural analysis by X-ray diffraction pattern showed as-deposited ZnO film has high-orientation along cdirection (0 0 2), which remained the same with low-intensity after heat treatment. Well-defined cones almost perpendicular to substrate surface, which were slightly compressed in size after heat treatment, have been detected through SEM micrographs. Water wettability study revealed a contact angle of 72.28 1.58 for as-deposited ZnO films, whereas hydrophobic surface with a contact angle of 152.84 1.58 was obtained after heat treatment. This is attributed to the topographical change in structural morphology. Change in bandgap energy from 3.7 to 3.2 eV was observed after heat treatment. Electrical resistivity measurement showed semiconducting nature with room temperature resistivity 104 V cm for as-deposited ZnO, which was decreased to 103 V cm for annealed ZnO film.