Effects of Co doping on structure and optical properties of TiO2 thin films prepared by sol-gel method

► Ti1 − xCoxO2 thin films (0 ≤ x ≤ 0.1) were fabricated by the sol-gel method. ► Increase in Co contents results in Raman shifts to lower frequencies. ► The packing density increases with increasing Co doping. ► The optical band gap increases and then decreases with the increasing Co content. ► The optical band gap varies between 3.1 and 3.26 eV.