Total Pressure and Annealing Temperature Effects on Structure and Photo-Induce Hydrophilicity of Reactive DC Sputtered TiO₂ Thin Films

Abstract

Nano-crystalline Titanium dioxide (TiO₂) has been well-known as a one of the most useful semiconductor material for application in self-cleaning coating which contains hydrophilic property. In this research, the films were deposited on un-heated silicon and glass slide substrates by home-made reactive unbalance magnetron sputtering system at various total gas pressures of 3.0 x 10^-3, 5.0 x 10^-3 and 7.0 x 10^-3 mbar, as deposited thin films of 7.0 x 10^-3 mbar annealed in the ambient air at 100^oC, 300^oC and 500^oC, respectively. The effect of total pressure and annealing temperatures on structure, surface morphology and hydrophilic properties were characterized by X-ray Diffraction (XRD), Atomic Force Microscope (AFM) and contact angle meter under UV illumination. The results reveal that the crystal structure, surface morphology and photo-induce hydrophilicity were strongly influence by total pressure and annealing temperature. The films showed mixed phase of rutile and anatase. The phase transition from rutile to mixed phase of anatase/rutile was observed with increase total pressure. In addition, the roughness increased from 2.1 to 5.3 nm which give a greater hydrophicity. The enhancement of crystallinity and hydrophilic properties were obtained by varied the annealing temperature. The phase mixture of anatase/rutite and annealed temperature of 300^oC show that the contact angle of thin film became 0^o after UV light irradiation which exhibited clearly superhydrohilic property.