Search

Abstract: Niobium-doped titania (TNO) films of various Nb content were deposited on glass and silicon substrates by reactive co-sputtering of Ti and Nb metal targets. Nb content in the TNO films was varied from 0 to ∼13at.% (atomic percent), corresponding to Ti1−x Nb x O2 with x =0–0.52, by modulating the Nb target power from 0 to 150W (Watts). The influence of ion bombardment on the TNO films was investigated by applying an RF substrate bias from 0 to 25W. The as-deposited TNO films were all amorphous and insulating, but after annealing at 600°C for 1h in hydrogen, they became crystalline and conductive. The annealed films crystallized into either pure anatase or mixed anatase and rutile structures. The as-deposited and the annealed films were transparent, with an average transmittance above 70%. Anatase TNO film (Ti1−0.39Nb0.39O2) with Nb 9.7at.% exhibited a dramatically reduced resistivity of 9.2×10−4 Ωcm, a carrier density of 6.6×1021 cm−3 and a carrier mobility around 1.0cm2 V−1 s−1. In contrast, the mixed-phase Ti1−0.39Nb0.39O2 showed a higher resistivity of 1.2×10−1 Ωcm. This work demonstrates that the anatase phase, oxygen vacancies, and Nb dopants are all important factors in achieving high conductivities in TNO films. [Copyright &y& Elsevier]