Structural and optical properties of Ti1−xCoxO2 films prepared by sol–gel spin coating

Ti1−xCoxO2 (x = 0–0.07) films were prepared by sol–gel spin coating and characterized by a variety of techniques. We mainly investigated the effect of Co dopant on the structural and optical properties of Ti1−xCoxO2 films. XRD studies showed that the magnetic Co impurity atoms were substituted for the Ti sites in rutile TiO2. Also, the FTIR spectra clearly showed the substitution of Co atom for Ti in TiO2, resulting in a disorder of the crystal structure and the presence of oxygen vacancies in Ti1−xCoxO2 lattice. By vibrating sample magnetometer (VSM) measurement, the films with x = 0.03, 0.05 and 0.07 were found to be ferromagnetic at room temperature. For the case of ferromagnetic Ti1−xCoxO2 films, an emission band in the range of 450–500 nm from oxygen vacancies at various energies was detected from the photoluminescence (PL) measurement. VSM and PL analyses showed that oxygen vacancies probably played a major role in ferromagnetism of the Ti1−xCoxO2 system with Co substituting for Ti.