Structural, electrical and optical properties of molybdenum-doped TiO2 thin films

Molybdenum doped TiO2 (MTO) thin films were prepared by radio frequency (RF) magnetron sputtering at room temperature and followed by a heat treatment in a reductive atmosphere containing 90% N2 and 10% H2. XRD and FESEM were employed to evaluate the microstructure of the MTO films, revealing that the addition of molybdenum enhances the crystallization and increases the grain size of TiO2 films. The optimal electrical properties of the MTO films were obtained with 3 wt% Mo doping, producing a resistivity of 1.1×10−3 Ω cm, a carrier density of 9.7×1020 cm−3 and a mobility of 5.9 cm2/Vs. The refractive index and extinction coefficient of MTO films were also measured as a function of film porosity. The optical band gap of the MTO films ranged from 3.28 to 3.36 eV, which is greater than that of the un-doped TiO2 film. This blue shift of approximately 0.14 eV was attributed to the Burstein–Moss effect.