Influence of thickness on the structural, morphological and optical properties of Co-doped TiO₂ thin films prepared by sol-gel method

TiO₂-based materials have high strength and suitable electronic properties that make TiO₂ widely used. In this research, Co-doped TiO₂ thin films were created through the sol-gel spin-coating method. The deposition process was conducted 3 times to prepare 1 to 3 layers. The structural, morphological, and optical properties of Co-TiO₂ thin films were explored by XRD, SEM, and UV-VIS analyses. The prepared films were amorphous without a crystalline structure. SEM images demonstrate highly uniform particles on the surfaces. With the rise of thickness, nanoparticles get closer, and the particle size decreases. EDS spectra verify the existence of Ti, O, and Co in all samples. The transparency of thin films was reduced by increasing the thickness. Bandgap energy decreased with increasing the deposition layers, while Urbach energy increased.