Paper TF-TuM10
Metal Ion Photoreduction on ALD Thin Films

Tuesday, October 29, 2013, 11:00 am, Room 104 A

Photoreduction of metal ions onto atomic layer deposited semiconducting surfaces are examined as a means for water reclamation/filtration and development of conductive patterns on polymeric substrates. Specifically, ZnO (via diethyl zinc/H₂O) and TiO₂ (titanium tetrachloride/H₂O) thin films are deposited on polymer film and fabric substrates and evaluated for reducing Ag⁺, Cr⁶⁺, As³⁺, and Au³⁺ from solution into metallic and oxidized coatings. The effect of ALD film thickness and process temperature on the efficiency of UV-light enabled reduction of the metal ions is evaluated. The effect of nucleation behavior of the metal ion reduction is explored and shows dependence on the surface structure and the impurity content in the ALD thin films. For example, reduction on ZnO with a characteristic nanoscale surface roughness shows a distinct nanoflake-like nucleation. On TiO₂, with a much lower surface roughness, island-like nucleation is exhibited. Both nano- and micro-scale islands are shown, likely due to corresponding reduction of Cl impurities from the TiO₂ film as observed by X-ray diffraction. Hard contact masks are applied onto the ALD thin films to explore the efficacy of producing conductive patterned structures directly on the ALD thin films. For applications in water filtration, ZnO ALD functionalization of high surface area fabrics have shown the ability to reduce up to 35% of Cr⁶⁺ and a dependence on the number of ALD cycles is observed. Results for As³⁺ and mixed metal ion solutions are also presented.