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

The persistent competition for the cost-efficient production of solar cells and displays requires low-cost and high throughput production of transparent conductive oxides (TCOs). Nbdoped titania (TiO2:Nb) is a promising novel TCO material for these applications. The results of investigations of TiO2:Nb thin films deposited on large area substrates by sputtering with high deposition rates are reported. The films have been deposited by direct current sputtering of a 780 mm long substoichiometric oxide tubular target arranged in a rotatable magnetron system in a pilot scale in-line sputtering plant. The films were grown on unheated substrates at different oxygen fractions in Ar/O2 atmosphere and then thermally annealed at temperatures of 450°C. The influence of the magnetron magnetic field strength and oxygen fraction in the sputtering gas on the properties and structure of TiO2:Nb was investigated. A resistivity of 9.4x10-4 ?cm, 82% transmittance in the visible range and a refractive index of ~2.5 (? = 550 nm) have been obtained on a film of the thickness 100 nm after annealing. For phase identification of the disordered structure, some as-deposited and annealed TiO2:Nb films have been investigated by X-ray absorption near edge structure spectroscopy (XANES).