Ti-TiO2 bilayer thin films were successfully prepared onto a glass substrate using magnetron sputtering with different TiO2 bottom layer conditions. These represent a lack of (as-deposited) and full oxygen content (annealed). Single-layer Ti was additionally used as a control. The influence of oxygen diffusion phenomena of the bottom layer of TiO2 to the upper layer of Ti thin films at different oxidation temperatures on structural, optical, and photocatalytic performance was investigated. X-ray diffraction (XRD) results confirmed that the crystalline phases coexisting on thin-film samples oxidized at 450 °C were TiO, TiO1.4, (bilayer, as-deposited TiO2), anatase (bilayer, annealed TiO2), and rutile (single and bilayer). This finding showed that the film’s phase structure evolution is significantly affected by oxygen diffusion from the bottom layer. Further increasing the thermal oxidation temperature caused a notable decline in the amorphous zone in bilayer thin films based on TEM analysis. Bilayer thin films lead to higher degradation of methylene blue under UV light radiation (63%) than single-layer films (45%) oxidized at 450 °C. High photocatalytic activity performance was found in the bilayer annealed TiO2-Ti thin-film sample. This study demonstrates that the bilayer modification strategy promotes the oxygen-induced bottom layer of TiO2 bilayer thin films.

A pure Ti target in Ar/O2 gas mixture was used to synthesize Ti3Ox thin film on a glass substrate by Reactive High-Power Impulse Magnetron Sputtering (HiPIMS) under different sputtering power (2 and 2.5 kW). The influence of HiPIMS parameters on thin films’ structural, morphological, chemical composition, optical and photocatalytic, and antibacterial properties was investigated. In this study, Ti3Ox thin films can be synthesized using the HiPIMS method without the post-annealing process. Two co-existence phases (hexagonal Ti3O and base-centered monoclinic Ti3O5 phases) existed on the Ti3Ox films. It is found that the peak intensity of (006) Ti3O hexagonal slightly increased as the sputtering power increased from 2 to 2.5 kW. The Ti3Ox thin-film bandgap values were 3.36 and 3.50 eV for 2 and 2.5 kW, respectively. The Ti3Ox films deposited at 2.5 kW showed good photocatalytic activity under UV light irradiation, with a higher methylene blue dye degradation rate than TiO2 thin films. The antibacterial study on Ti3Ox thin films exhibited a high inhibition percentage against E. coli and S. aureus. This study demonstrates that Ti3Ox thin films can promote high photocatalytic and antibacterial activity.