Phase transformation from rutile to anatase with oxygen ion dose in the TiO2 layer formed on a Ti substrate

The oxygen plasma immersion ion implantation (O-PIII) method was used to form a TiO2 layer on a Ti substrate. The content of the anatase polycrystalline phase increased from 5.1% to 22.3% of the total TiO2 amount with a higher O+ ion dose. The oxygen ion doses were 3.6 x 10(16) ions, 8.1 x 10(16) ions, 1.26 x 10(17) ions, for 1, 2, and 3 h, respectively, with ion energies of E approximate to 0.8 keV. The polycrystalline phases and morphology of the obtained films were characterized by XRD, FESEM, AFM, and Raman spectroscopy. The chemical bond analysis and layerby-layer measurements for TiO2 layer thickness evaluation were performed by XPS. The photocatalytic decomposition reaction constants of a methylene blue solution increased from 3.2 x 10(-3) min(-1) to 4.2 x 10(-3) min(-1) under UV-A irradiation and the liquid free surface energy increased from 39.0 mJ/m(2) to 49.5 mJ/m(2) with a higher O-PIII treatment doses. These results were explained by the partial phase transition of the TiO2 layer from rutile to anatase. Thus, the increase in the O+ ions implantation dose into the Ti substrate invoked the reduction of material density from Ti (rho = 4.506 g/cm(3)) through TiO2 rutile (4.23 g/cm(3)) to TiO2 anatase (3.78 g/cm(3)) phase.