Doping concentration effects upon column-structured Nb:TiO2 for transparent conductive thin films prepared by a sol-gel method

The column-structured Nb-doped TiO2 (TNO) films with various Nb concentrations in the range between 0 and 10 at.% have been prepared by a sol-gel method. The phase compositions, element concentrations, microstructures, and optical-electron properties have been characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, electron microscopy, and UV/Vis/Near-IR spectrophotometer. The experimental results show that all of the samples prepared in the present work exhibit column-structured morphology and Nb doping concentration has a non-monotonic effect upon the microstructure. The relatively low conductivity and high transmittance of the samples demonstrate that column-structured microstructures greatly improve the optical and electronic properties of TNO films. The favorable sample with 10 at.% Nb doping concentration exhibits a resistance of about 2.27 Ω cm and transmittance of approximately 68.78% with 85 nm thickness.