Deposited Tio₂ thin films by atomic layer deposition (ALD) for optical properties

The thin films ceramic oxide can be fabricated by ALD because this technique promises to control the deposition on an atomic scale by sequentially dosing the surface with appropriate chemical precursors, and by promoting surface chemical reactions that are inherently self-limiting. TiO₂ has been widely used in photocatalysts, due to its photosensitivity and thermal stability. TiO₂ also has strong absorption in the UV range, at around 3.3 eV. ALD deposition cycle and temperature would determine the surface morphology of TiO₂ thin films from a very smooth surface to a rough surface, which is important for their functional applications. The combined results of XRD and AFM show that the deposition temperature played an important role in the growth of TiO₂ thin films and the phase transition from amorphous to anatase. These results demonstrated a self-limiting of 0.017 - 0.024 nm/cycle growth of the TiO₂ thin films using TTIP and H₂O, at deposition temperatures ranging from 100°C to 300°C. The optical properties of TiO₂ thin films were also influenced by the deposition temperature. In addition, UV luminescence (at 353 nm) was present in the TiO₂ thin films deposited at 200°C whereas there was no UV luminescence for pure bulk TiO₂.