Recent developments of TiO2:Nb sputtered with high deposition rates from a rotatable magnetron system

The persistent competition for the cost-effective production of solar cells and displays requires low cost and high throughput production of transparent conductive oxides (TCOs). Nb-doped titania (TiO2:Nb) is a promising novel TCO material for these applications. The results of investigations of TiO2:Nb thin film deposited on large area substrates by sputtering with high deposition rates are reported. As a deposition method we used the direct current sputtering of a 780 mm length substoichiometric oxide tubular target arranged in a rotatable magnetron system in a pilot scale inline sputtering plant. The films were grown on unheated substrates and then thermally annealed at temperatures of 450°C. The influence of the magnetron magnetic field strength and oxygen partial pressure in the sputtering gas on the properties and structure of TiO2:Nb was investigated. A 100 nm thin film deposited on Borofloat® substrate shows after annealing a resistivity of 9.4 x 10-4Ωcm, 82% transmittance in the visible range and a refractive index of ~2.5 (λ=550 nm). The film properties were compared with those of the films grown using a planar oxidic target.