Synthesis and properties of TiO2 thin films by plasma source ion implantation

Plasma source ion implantation was used to prepare anatase type photocatalytic TiO2 films on silicon wafer and quartz glass from titanium tetraisopropoxide as a precursor. RF power was used to produce a glow discharge plasma. High negative voltage pulses of −20 kV, repetition rate 100 Hz and 1 kHz were applied to the substrate holder to accelerate ions from the plasma. After the deposition, the films were annealed for 1 h in air at a constant temperature from 673 to 1023 K. The films were analyzed by XRD, XPS and Raman spectroscopy. The photocatalytic property of TiO2 films was evaluated by examining the decomposition of an aqueous solution of methylene blue under UV irradiation. XPS and Raman results showed that the deposited films consisted of Ti, O and C and an amorphous carbon structure. The color of the films changed from black to colorless and transparent after annealing at a temperature above 723 K. XPS results showed that the composition of the films annealed at 873 K was stoichiometric TiO2. The formation of a single phase anatase type TiO2 crystalline was confirmed for the films annealed between 723 and 923 K by XRD and Raman measurements. The films annealed at 973 K were a mixture of anatase and rutile type crystals. The film annealed at 973 K had the highest photocatalytic activity for the decomposition of aqueous solution of methylene blue.