Development of Rutile Titanium Oxide Thin Films as Battery Material Component Using Atomic Layer Deposition

摘要

Herein, growth kinetics, crystal structure, and the uniformity of titanium oxide (TiO_2) thin films prepared using atomic layer deposition (ALD) and plasmaenhanced ALD (PE-ALD) are studied. TiO_2 thin films are grown using titanium tetrachloride (TiCl_4), water, and oxygen precursors. Using ALD, TiO_2 is grown in the temperature range of 270–310°C thermally and in the range of 300–400°C with PE-ALD. In spite of the plasma process yielding better uniformity on planar structures, the optimized thermal process provides a remarkable conformal step coverage within deep trenches. In addition, the change in the crystal structure and phase transitions of TiO_2 is presented herein. This is attempted at using TiO_2 as a component material to grow lithium titanate (LTO) as an electrode material in solid-state lithium-ion batteries (LIBs). Thereby, different substrates are used. In comparison to the silicon (Si) substrate, silicon oxide (SiO_2) and titanium nitride (TiN) lead to crystal phase transformation while annealing. Measurements are performed using in situ high-temperature X-ray diffraction (HT-XRD). It is also shown that when TiN is sandwiched between TiO_2 and the silicon substrate, the TiO_2 thin film (25 nm) gradually changes from an anatase to a rutile structure.