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

Abstract

Films of the Zr_1–xTi_xO₂ 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 SiO_2–x microropes), the formation of a tetragonal phase in ZrO₂ films was reliably identified. A sharp increase in the refractive index from \({{n}_{{{\text{Zr}}{{{\text{O}}}_{2}}}}}\) = 2.09 to n_ZTO = 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.