Fabrication of conductive Nb-doped anatase TiO2 thin films by mist chemical vapor deposition using aqueous solutions of water-soluble Ti and Nb compounds

Abstract

Electrically conductive Nb-doped anatase TiO₂ (Ti_1−x Nb _x O₂: TNO) films can be fabricated through mist CVD using aqueous precursor solutions of water-soluble oxo-peroxo-glycolato titanium complex and ammonium niobium oxalate. Post-deposition annealing in vacuum crystallizes the as-deposited amorphous films into a conductive anatase phase, leading to the fabrication of conductive TNO films. Notably, the addition of H₂O₂ to the precursor solutions enhances both the crystallinity and conductivity of the annealed TNO films. A Ti_0.77N_0.23O₂ film, annealed at 700 °C, exhibits a resistivity of 2.0 × 10⁻² Ω cm at ambient temperature. In general, the solution-based fabrication of TiO₂ films relies on organic solvents, which are sometimes toxic and explosive. Here, we demonstrate for the first time that conductive TNO films can be prepared from less toxic and nonflammable aqueous solutions. These findings mark a significant advancement towards a more environmentally compatible process for fabricating TNO films with sufficient conductivity.