Remote plasma sputtering deposited Nb-doped TiO2 with remarkable transparent conductivity

Nb-doped TiO2 (TNO) thin films with high electrical conductivity and excellent transparency were fabricated for the first time by reactive remote-plasma sputtering deposition. TNO films were deposited on non-alkali glass slides at room temperature, using a reactive remote plasma sputtering technology, followed by low-temperature annealing in ambient air. The as-deposited films were amorphous which were then crystallised into anatase nanocrystals after a short thermal exposure of 30 min at a moderate temperature of 280 °C. Such low temperature crystallisation induced remarkable enhancement of both conductivity and transparency, with the annealed samples demonstrating low resistivity of 6.4×10−4 Ω cm at room temperature and up to 87% optical transmittance. Fundamentally, the excellent transparent conductivity from the current work is attributed to the interplay between doping Nb to the Ti sub-lattice sites of the anatase phase and energetic/electronic effects due to formation of native defects. The achieved optical transparency and electrical conductivity for TNO are comparable to those for tin-doped indium oxide (ITO), thus demonstrating great potential in low-carbon processing of TNO to substitute the ITO that is based on the depleting and expensive indium resource.