A facile route to prepare ZnO super-hydrophobic surface with hierarchical structure

Zn oxide film with the special hierarchical structure, consisting of microspheres and nano-nets, has been successfully fabricated by a two-step solution approach on a sapphire substrate. The surface chemistry and morphological features were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). X-ray diffraction pattern (XRD) shows that all diffraction peaks can be indexed to those of the hexagonal wurtzite phase of Zn oxide and no other phases were detected. Transmittance measurements show that the optical transmittance of the sample synthesized at 720 deg. C on the sapphire substrate is about 73% in the visible light wave band. The water repelling characteristics of the film were measured by the snapshots with a Hitachi camera, and the measurement shows the water has a contact angle (CA) of about 151.3 deg. as well as a small sliding angle (SA) of about 6o. The above measurements indicate that the Zn oxide film has the super-hydrophobic property.