Photo-activity of doped/undoped nanostructured titanium oxide thin film deposited via RF Magnetron Sputtering

The photo-activity of doped/undoped titania have been widely investigated from years and is actually exploited in many fields: photovoltaic energy productions1, hydrogen production by water splitting2, photo-cathodic protections of metals3, photodegradation of bio-organics and inorganic pollutants4. The titania physical-chemical behavior is strongly related on phase (anatase or rutile), microstructure and stoichiometry and several preparation methodologies were fit out to control these parameters. In this presentation some results will be reported on the achievement of undoped and nitrogen doped anatase and anatase/rutile thin films, deposited by RF magnetron sputtering in reactive atmosphere from a Ti target (99,9% purity). To tune the titania thin film phases, power supply, pressures of gas inlet in the deposition chamber were carefully adjusted and substrate temperature and movement controlled during the deposition process. Moreover, substrate temperature and movement were carefully controlled during the deposition process. Nanostructured thin films were deposited with the selected allotropic structure, as showed by XRD analysis, at suitable rate (about 3÷4 nm/min) without thermal post-treatment. The stoichiometry of the doped samples was monitored by XPS analysis. Voltammetric and impedance spectroscopy studies in the both cases show the photocatalytic activity under UV irradiation. Under intermittent condition, the current - potential characteristics of Ti -covered TiO2 electrodes are subject to strong transient effect with relaxation time in order of several minutes. The impedance response was used for examine the existence of the surface states and their modification in several aqueous electrolyte solutions and characterize energy levels in semiconductors. Moreover, we will briefly describe the specific PVD instrumental set-up and, in particular, the motorized, temperature-controlled, sample holders realized to obtain homogeneous thin films of required phases.