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

Abstract

We have investigated the surface reaction mechanisms during the atomic layer deposition (ALD) of TiO2 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 CO2. The growth rate, ∼0.52 Å/cycle, is almost independent of the substrate temperature between 150 and 250 °C.