Chemical and Phase Composition, and Optical Properties of Zirconium-Titanium Oxide Coatings Synthesized by Atomic Layer Deposition

Films of the Zr1–xTixO2 system (0 ≤ x ≤ 1) with a thickness of 35–50 nm were synthesized by atomic layer deposition at 250°C using a novel precursor combination: tetrakis(ethylmethylamido)zirconium(IV) (TEMAZ) and titanium(IV) tetrachloride (TiCl4) with water vapor. It was shown that the growth of mixed oxides is characterized by a noticeable (30–40%) decrease in the average growth per cycle by compared to the rule of mixtures. Chemisorption reactions of both TEMAZ and TiCl4 molecules are inhibited. The chemical composition of the films depends linearly on the cycle ratio in the supercycle. SEM and X-ray powder diffraction revealed a dependence of crystallinity and morphology on the composition. Using high-surface-area substrates (arrays of oriented SiO2–x microropes), the formation of a tetragonal phase in ZrO2 films was reliably identified. A sharp increase in the refractive index from n_ZrO₂ = 2.09 to nZTO = 2.20 was observed with minimal doping of ZrO2 with titanium (~2–3 at %). The results may be useful in the development of materials with specified optical properties.