Preparation of TiO2 thin films deposited from highly dense targets with multi-oxide glass doping

Glass doped TiO2 (GTO) thin films were deposited by radio frequency (RF) magnetron sputter at room temperature and annealed in a reductive atmosphere containing 90 % N2 and 10 % H2. Highly dense TiO2 ceramic mixed with glass consisting of multi-metal oxides (as a sintering aid) was used as the sputtering target. This sintering aid allows low temperature densification of TiO2 target through a liquid phase wetting mechanism, and also works as a doping resource. XRD and FESEM were carried out to characterize the microstructure of the GTO films and the results reveal that the doping of multi-metal ions enhances the crystallization and increases the grain size of TiO2 films. TEM analysis also showed that these metal ions were dissolved into TiO2 lattices. The electrical and optical properties of TiO2 thin films at different glass concentrations were evaluated and compared to the films merely doped with MoO3. The electrical resistivity of the GTO films reaches 9.1 × 10–4 Ω·cm at 2 wt% glass doping, corresponding to a carrier density of 8.9 x 1020 cm-3 and a mobility of 7.1 cm2/Vs. Meanwhile, the electrical resistivity of the TiO2 film doped with glass was found to be lower than that of MoO3-doped film. This was mainly attributed to the increase in carrier concentration by double doping effect of glass. The optical band gap of the GTO films ranged from 3.34 to 3.42 eV, which is greater than that of the un-doped TiO2 film. This blue shift of approximately 0.18 eV was due to the Burstein-Moss effect.