Sputtered Nb- and Ta-doped TiO2 transparent conducting oxide films on glass

Abstract

Radio frequency (rf) magnetron sputtering is used to deposit Ti0.85Nb0.15O2 and Ti0.8Ta0.2O2 films on glass substrates at substrate temperatures (TS) ranging from ∼250 to 400 °C. The most conducting Nb-doped TiO2 films were deposited at TS = 370 °C, with conductivities of ∼60 S/cm, carrier concentrations of 1.5 × 1021 cm−3 and mobilities <1 cm2/V·s. The conductivity of the films was limited by the mobility, which was more than 10 times lower than the mobility for films deposited epitaxially on SrTiO3. The difference in properties is likely caused by the randomly oriented crystal structure of the films deposited on glass compared with biaxially textured films deposited on SrTiO3. The anatase phase could not be stabilized in the Ta-doped TiO2 films, likely because of the high dopant concentration.