Defect-Mediated Crystallization of the Particulate TiO2 Photocatalyst Grown by Atomic Layer Deposition

High Resolution Image Download MS PowerPoint Slide Nanopowders or films of pure and mixed oxides in nanoparticulate form have gained specific interest due to their applicability in functionalizing high-surface-area substrates. Among various other applications, our presented work primarily focuses on the behavior of TiO 2 as a photocatalyst deposited by atomic layer deposition (ALD) on a quartz particle. The photocatalytic activity of TiO 2 on quartz particles grown by ALD was studied in terms of ALD growth temperature and post-treatment heating rate. Amorphous TiO 2 thin films (30 nm) were grown from tetrakis(dimethylamido)titanium (TDMAT) at 100 and 200 °C on quartz particles (0.35–3.5 μm) and crystallized using oxidative heat treatment at 500 °C with variable heating rates. The growth temperature was found to affect the TiO 2 defect structure: TiO 2 grown at 200 °C is black due to Ti 3+ defects, whereas the film grown at 100 °C is white but contains some traces of the TDMAT ALD precursor. During the oxidative heat treatment, precursor traces desorbed and Ti 3+ defects were oxidized. ALD TiO 2 grown at 100 °C crystallized as anatase, whereas the rutile-to-anatase ratio of 200 °C grown TiO 2 increased with the heating rate. The hydrogen production rate of mixed-phase TiO 2 was found to outperform that of anatase TiO 2 .