Highly Reactive TiO₂ Anatase Single Crystal Domains Grown by Atomic Layer Deposition

Anatase TiO₂ films with unusual domains-like morphology were obtained by postdeposition annealing of amorphous TiO₂ films deposited by atomic layer deposition (ALD). Such particular morphology was observed only for TiO₂ films deposited using TiCl₄ precursor in a nonconventional ALD regime where the reaction byproducts or nonreacted precursors are incorporated into the film and induce an explosive recrystallization upon annealing. This recrystallization leads to the formation of micrometric single crystal domains. The investigation of domains by electron backscatter diffraction shows the formation of a significant amount of highly reactive anatase crystalline facets such as (111) that contradicts fundamental crystal growth rules. The stabilization of (111) facets in films without additional seed layers has a strong interest for photocatalysis-based applications for environmental remediation or hydrogen production.