Aerosol assisted chemical vapor deposition of conductive and photocatalytically active tantalum doped titanium dioxide films

Abstract

This paper shows the aerosol assisted chemical vapour deposition of transparent, blue coloured and conductive tantalum doped titanium dioxide films from the CVD reaction of Ti(OEt)₄ and Ta(OEt)₅. Hall effect measurements showed the doped films to have excellent n-type electrical conductivity showing, to the best of our knowledge, the lowest reported sheet resistance ever recorded for Ta-doped TiO₂ of 14 Ω sq⁻¹. The Ta 6 atom% doped TiO₂ film also showed the best electrical results with a charge carrier concentration of 1.60 × 10²¹ cm⁻³ and mobility of 1.44 cm² V⁻¹ s⁻¹ making it a suitable electrode in photovoltaic devices. The doped films were multifunctional, showing good photocatalytic activity under UV-light illumination. XPS and XRD studies gave strong evidence that the Ta was entering the TiO₂ lattice as Ta⁵⁺ and that a reduction of some Ti⁴⁺ to Ti³⁺ was observed.