Effect of cobalt doping and annealing on properties of titania thin films prepared by sol-gel process

► Cobalt in the cobalt doped TiO2 thin films was mainly in Co2+ oxidation state. ► CoTiO3 was discovered in the cobalt doped TiO2 films after annealing above 650 °C. ► During annealing cobalt compounds segregate to the surface of samples. ► EDX analysis showed that “islands” of cobalt compounds are formed in the sample. ► Cobalt doping red-shifted the fundamental absorption edge compared to virgin titania.