Low energy ion-beam modification of TiO2 photocatalyst thin film for visible light absorption

Photocatalytic reaction of activated TiO2 can be directly used for water splitting to produce hydrogen for fuel cell. TiO2 thin films have been deposited using sol–gel method and subsequently heat-treated at 500 °C to form anatase phase. Ar+ or N+ ions with energy of 30 keV were implanted in anatase TiO2 thin films with different ion doses in order to modify the band gap for visible light absorbance. UV–Vis spectroscopy was used to check the efficiency for absorbing visible light while structural and surface modifications caused by implantation were studied by using FT-IR and SEM respectively in the TiO2 films. The ion-beam modified samples were found to be more efficient to absorb visible light in comparison to pure TiO2 films. This efficiency of absorption increases with the implantation dose without any structural changes studied from FT-IR analysis. Ar+ ions caused the formation of defect energy levels in the band gap while N+ ions efficiently narrowed the band gap of TiO2 thin film in the visible light region. The results are further discussed in terms of defect formation caused by ion implantation.