Tuning the crystallization temperature of titanium dioxide thin films by incorporating silicon dioxide via supercycle atomic layer deposition

Titanium oxide-based nanomaterials are nowadays of great interest in various application fields such as optics, sensing, photocatalysis, and solar cells. Tuning their physical properties by tailoring the geometry or combining them with different materials further expands their applicability and even allows for the generation of new functionalities. The materials’ crystalline phase also determines its properties and the crystallization behavior can be modified by doping or multilayering thin films with various materials. For instance, the combination of TiO2 with silicon dioxide (SiO2) renders these composites ideal candidates for coatings applied in harsh environments based on the high chemical and mechanical stability of both materials. Applying such coatings in optics, sensing, or photocatalysis require accurate prediction of the evolution of their properties and crystalline phase during heat treatments within the fabrication and application. Herein, we present the fabrication of SiO2-incorporated TiO2 thin films by supercycle atomic layer deposition (ALD). Specifically, TiO2-SiO2 multilayers with varying material ratios, TiO2 thicknesses, and individual layer numbers as well as SiO2-doped TiO2 thin films are prepared. Their crystallization behavior is studied by in situ X-ray diffraction during thermal annealing. The structural properties of the composite materials are assessed by X-ray reflectivity, spectroscopic ellipsometry, and transmission electron microscopy before and after annealing. TiO2-SiO2 multilayers show increasing crystallization temperatures from amorphous TiO2 to anatase with decreasing TiO2 layer thickness from 50 nm to 4 nm and with increasing number of TiO2 layers. Their layered structure is retained during annealing while the interfaces roughen slightly. SiO2-doped TiO2 thin films demonstrate increasing crystallization temperatures with increasing SiO2 contents up to 10 %. The refractive index of these doped structures is tailored by the SiO2 content. Detailed characterization of ALD deposited SiO2-containing TiO2 thin films could further expand their application in the future by precisely adjusting the fabrication process for the desired material properties and target application.

Subjects

Atomic layer deposition | Crystallization | Phase transition | Titanium dioxide

DDC Class

600: Technology

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publishedVersion

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https://creativecommons.org/licenses/by/4.0/

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Tuning-the-crystallization-temperature-of-titanium-dioxide-th_2025_Surfaces-.pdf

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8.94 MB

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Tuning the crystallization temperature of titanium dioxide thin films by incorporating silicon dioxide via supercycle atomic layer deposition