Post-deposition annealing effects on the transparent conducting properties of anatase Nb:TiO2 films on glass substrates

• Vacuum annealing effects on the properties of anatase Nb:TiO2 films on glass.
• Phase transformation from amorphous to anatase by vacuum annealing above 350 °C.
• Minimized resistivity and maximized mobility in the Nb:TiO2 film annealed at 450 °C.
• Increase in the optical band gap of Nb:TiO2 with increase of the annealing temperature.

Five percent Nb-doped TiO2 (Nb:TiO2) films on glass substrates were prepared with pulsed laser deposition in 10 mTorr at room temperature, and then, they were annealed at various temperatures from 250 to 550 °C in vacuum (<10−5 Torr). The X-ray diffraction data suggest that the as-prepared amorphous Nb:TiO2 film on glass was transformed to the (1 0 1) oriented anatase phase above ∼350 °C. For the anatase Nb:TiO2 samples, the temperature dependence of the resistance exhibited a metallic behavior. As the post-deposition annealing temperature increased up to 550 °C, the resistivity (∼3.9 × 10−4 Ω cm) was minimum at 450 °C while the Hall mobility (2.6 cm2/(V s)) and carrier density (4.7 × 1021 cm−3) were maximum. The optical transmittance in the visible light range was about 70–80%, and the optical band gaps gradually decreased from 3.64 to 3.28 eV as the post-deposition annealing temperature increased.