The effect of process parameters on the structure, photocatalytic and self-cleaning properties of TiO2 and Ag-TiO2 coatings deposited using reactive magnetron sputtering

• TiO2 and Ag-TiO2 coatings are reactively sputtered at commercially-viable rates.
• The morphology and structure of coatings is controlled by deposition parameters.
• It was possible to achieve as-deposited crystalline and photocatalytic coatings.
• Annealing had a deleterious effect on mechanical and photocatalytic properties.
• Initial evaluation of Ag-TiO2 coatings showed antimicrobial effect against E. coli.

This article reports on the morphology, structure, wettability, photocatalytic and mechanical properties of TiO2 and Ag-TiO2 thin films, with the latter also displaying antimicrobial activity. The coatings were deposited using reactive closed field unbalanced magnetron sputtering. It was possible, by varying the process parameters, to tailor the structure and composition of the coatings. TiO2 coatings which were deposited from a single titanium target (thickness ~ 1 μm) were relatively dense with low crystallinity and a mixed anatase and rutile structure. The addition of silver resulted in the formation of submicron sized silver particles dispersed throughout the coating. TiO2 coatings deposited from two titanium targets (thickness ~ 2 μm) had a mixed anatase and rutile structure with a less dense topography. Ag-TiO2 coatings deposited using this process showed a uniform dispersion of silver throughout the coating. All coatings presented excellent adhesion to the substrate and high photocatalytic activity under fluorescent light. Annealing at 600 °C had a detrimental effect on the photocatalytic activity as well as the mechanical properties of the coatings. The coatings deposited from a single Ti target were evaluated for their antimicrobial potential against E. coli. No reduction in the number of bacteria was observed using TiO2. Ag-TiO2 coatings, however, showed antimicrobial properties in the dark as well as light conditions, as a result of the innate antimicrobial potential of silver.