Transparent conductive Nb-doped TiO2 films deposited by direct-current magnetron sputtering using a TiO2 − x target

Nb-doped anatase TiO2 films were deposited on unheated glass by dc magnetron sputtering using a slightly reduced TiO2 − x target (2 − x = 1.986; conductivity, 3.7 S cm− 1; density, 4.21 g/cm3) with Nb2O5 pellets on it. After post-annealing in a vacuum (6 × 10− 4 Pa) at 400 °C for 1 h, these films were crystallized into a polycrystalline anatase TiO2 structure. The resistivity of the films decreased to 1.3 × 10− 3 Ω cm with increasing Nb concentration up to 6.4 at.%, where the carrier density was 1.3 × 1021 cm− 3 and the doping efficiency was estimated to be 65%. Such films exhibited high transparency of over 60–70% in the visible light region.