This work presents a study of the structural and optical properties of cobalt-doped titanium dioxide thin films prepared via the DC Magnetron Co-Sputtering technique using TiO2 and Co targets with 99.99% purity; these thin films were deposited on three different substrates: Soda-lime glass, titanium foil and silicon wafer. The resulting films deposited on glass were then submitted to annealing processes at temperatures ranging from 500 degrees C to 600 degrees C. X-ray diffraction measurements revealed limited crystallization of the as-deposited samples, whilst the annealed samples showed several crystalline phases, including cobalt oxide (Co3O4) and a ternary phase (CoTi2O5); SEM studies helped to corroborate that the inclusion of TiO2 into the thin film decreases its crystallinity, obtaining nanostructures smaller in size as compared with samples containing cobalt. UV-vis-NIR measurements revealed an increase in transparence of the thin films after annealing at 600 degrees C, evidencing extrinsic absorption phenomena, consistent with the formation of binary phases inside the semiconductor matrix. From XPS measurements, the oxidation states for Co and Ti were obtained. (C) 2018 Elsevier B. V. All rights reserved.