Investigation of effect of doping concentration in Nb-doped TiO2 thin films for TCO applications
2017
Singh, Satyavir | Sharma, Vikas | Sachdev, Kanupriya
Nb-doped TiO₂ (referred hereafter as NTO) thin films were deposited by sol–gel spin coating method to investigate their use as transparent conducting electrode (TCE). A range of Nb ₓ Ti₁₋ₓ O₂ (x = 0, 0.003, 0.005, 0.008, 0.01, 0.015, 0.02) compositions were synthesized and deposited as thin films via spin coating. The films were deposited at room temperature and showed crystallization on annealing at 550 °C for 1 h in air. The X-ray diffraction confirms formation of anatase TiO₂ by showing dominant peak at 2θ ~25.5° corresponding to (101) reflection plane. Raman spectroscopy shows the characteristics modes of TiO₂. Surface topography and morphology measured by atomic force microscopy and field-emission scanning electron microscopy exhibit smooth and uniform deposition of films. Optical transmittance reduces from 85 to 70% as Nb content increases from 0 to 2 at.%. Meanwhile, electrical resistivity attained a minimum value of 3.65 Ω cm for 2 at.% Nb doping. X-ray photoelectron spectroscopy analysis exhibits shifting of Ti 2p peak which confirms substitution by Nb⁵⁺ in TiO₂ lattice and Nb–O–Ti bond formation. Transmission electron microscope and selected area electron diffraction patterns reveal that films consist of Nb and crystalline phase of TiO₂. All films were characterized by Fourier transmission infrared spectroscopy and thermogravimetric analysis. Present study reports low-cost and effective fabrication of TCE for optoelectronic applications.
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