Atomic layer deposition of Nb-doped TiO2: dopant incorporation and effect of annealing

Transparent conductive oxides form an important group of materials that combine high conductivity with high transparency. In this context, the authors designed an atomic layer deposition process for Nb-doped TiO2. The presented process enables accurate control over both the position and concentration of the Nb dopants. The as-deposited films become crystalline (brookite) and low resistive (4.3 × 10−3 Ω cm) upon a postdeposition anneal with temperatures as low as 300 °C. Variations in annealing ambient and temperature yielded resistivity changes over four orders of magnitude and significant changes in the sub-bandgap absorption of light. Next to doping, annealing is therefore shown to be a powerful tool in controlling electrical and optical properties of TiO2:Nb.