Tailoring the structural and optical properties of TiO2 thin films: A study of undoped, N-doped, and Fe-doped variants via sol-gel spin coating

In this study, pristine, nitrogen-doped, and iron-doped TiO 2 films were individually prepared using the sol-gel spin coating method, focusing on analyzing their structural, morphological, and optical properties. Both undoped and doped TiO 2 thin films had been deposited on glass substrates and annealed at 500 °C. The structural characteristics of the films were examined through XRD, which confirmed their crystalline nature, with a preferred growth orientation along the (101) plane. Doping with nitrogen and iron individually caused variations in dislocation density, crystallite size, and micro strain. EDS verified the presence of the required elements. Optical properties were assessed using UV–vis spectroscopy over a wavelength range of 200–900 nm. Nitrogen doping resulted in a significant reduction in the band gap, while iron doping led to a smaller reduction. The nitrogen-doped TiO 2 films exhibited a higher absorption coefficient and extinction coefficient compared to the iron-doped films.