Low-Temperature Route to Direct Amorphous to Rutile Crystallization of TiO₂ Thin Films Grown by Atomic Layer Deposition

The physicochemical properties of titanium dioxide (TiO2) depend strongly on the crystal structure. Compared to anatase, rutile TiO2 has a smaller bandgap, higher dielectric constant, and refractive index, which are desired for thin films in many photonic applications. Unfortunately, fabrication usually requires temperatures that too high (>400 °C, often even 600–800 °C) applications involving, e.g., temperature-sensitive substrate materials. Here, we demonstrate atomic layer deposition (ALD)-based anatase mediated by precursor traces oxide defects, controlled ALD growth temperature when using tetrakis(dimethylamido)titanium(IV) (TDMAT) water as precursors. Nitrogen within amorphous titania grown at 100 °C inhibit nucleation until 375 stabilize phase. In contrast, (200 leads low nitrogen concentration, degree mass density facilitating direct an exceptionally post annealing (PDA) 250 °C. mixed-phase (rutile–brookite) film with primary phase forms upon PDA 250–500 allows utilization broad range