Enhanced optical and electrical properties of Nb-doped TiO2 thin films synthesized by atomic layer deposition using the supercycle strategy

Abstract

Herein, we report highly transparent and conductive Nb-doped TiO2 thin films successfully grown by a thermal ALD process at 300 °C using titanium tetraisopropoxide, niobium(V) ethoxide, and water. The deposition was carried out by employing a supercycle approach, alternating cycles of Ti precursor followed by a monocycle of Nb precursor, thereby enabling precise control over the Nb dopant concentration. We demonstrate the crucial impact of the dopant concentration and annealing conditions played on the thickness, structure, morphology, composition, and optical and electrical properties of the resulting films. The incorporation of niobium dopants led to significant improvements in the film's characteristics. The Nb-doped TiO2 films exhibited an enhanced optical transmission efficiency up to 15 %, along with a remarkable reduction in resistivity by four orders of magnitude, reaching 10−3 Ω.cm, compared to undoped TiO2 films. These high performances establish Nb-doped TiO2 thin films as promising TCOs with wide-ranging applications in fields that require efficient current collection or injection in conjunction with optical radiation transmission.