Effects of Total Pressure and Ar/O₂ Flow Ratios on Photocatalytic Properties of TiO₂ Thin Films Deposited by Direct Current Facing-Target Magnetron Sputtering

Abstract

Polycrystalline TiO2 thin films were prepared by direct current facing-target magnetron sputtering at different sputtering pressures and Ar/O2 flow ratios. The average thickness of all prepared films was 200 nm, measured by surface roughness tester. With increase in sputtering pressure (ptot), the prepared films changed from mixtures of anatase and rutile phases to pure anatase. The influences of different sputtering pressures and Ar/O2 flow ratios on surface morphology of prepared films were investigated by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The film surface was found to become rougher with increasing pressure and Ar/O2 flow ratios. Photocatalytic activities of the prepared TiO2 thin films were investigated by decomposition of iso-propanol (IPA) with initial concentration of 100×10-6 (volume fraction) under UV irradiation. The IPA was oxidized to acetone and further to carbon dioxide. TiO2 thin film deposited at 2.0 Pa with an Ar/O2 flow ratio of 1:1 showed the highest photocatalytic activity and maintained a high stability constant during the reaction.