Surface Reaction Mechanisms during Ozone-Based Atomic Layer Deposition of Titanium Dioxide

We have investigated the surface reaction mechanisms during the atomic layer deposition (ALD) of TiO 2 using titanium tetraisopropoxide (TTIP) and ozone using in situ attenuated total reflection Fourier transform infrared spectroscopy. The ozone reaction mechanism is fundamentally different than water-based ALD of metal oxides, where −OH groups are the reactive sites for metal alkoxides. In ozone-based ALD, the isopropoxy-ligand-terminated surface, generated after TTIP exposure, reacts with ozone, forming different surface carbonates. Upon subsequent TTIP exposure, the isopropoxy ligands chemisorb on the surface carbonates, releasing CO 2 . The growth rate, ∼0.52 Å/cycle, is almost independent of the substrate temperature between 150 and 250 °C.