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

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.