Ultraviolet shielding with tunable optical transparency using non-periodic TiO2–ZnO multilayers

• Tunable UV reflectance via non-periodic TiO 2 -ZnO multilayers grown by ALD. • Optical properties are adjusted by controlling the ratios of ultrathin layer thicknesses. • These multilayers exhibit high thermal stability after rapid thermal processing (RTP) at 500 °C. • Transmittance decreases monotonically in the UV region, making it ideal for ultraviolet shielding coatings. • Experimental results and TMM simulation data show excellent agreement in optical performance. We report the development of tunable ultraviolet reflectors based on non-periodic multilayer stacks of semiconductor oxides with nanoscale precision. Using thermal Atomic Layer Deposition, we fabricated. TiO 2 –ZnO bilayer stacks with individual layer thicknesses as thin as 1 nm, enabling precise optical control through tailored layer sequences. Three distinct configurations were investigated: 1 nm TiO 2 -5 nm ZnO, 5 nm TiO 2 -1 nm ZnO, and 5 nm TiO 2 −5 nm ZnO. To explore thermal stability and its effects on optical performance, the structures were subjected to Rapid Thermal Processing at 500 °C for 10 and 20 min in a nitrogen atmosphere. Remarkably, the multilayers retained strong UV reflectance after annealing, demonstrating robustness under high-temperature conditions, which is an essential criterion for practical UV shielding applications. Optical measurements were complemented by numerical simulations using the analytical transfer matrix method, showing excellent agreement with experimental results. Structural and morphological characterizations were performed via Transmission Electron Microscopy, Field-Emission Scanning Electron Microscopy, X-ray Diffraction, and Atomic Force Microscopy. Our results highlight the versatility of non-periodic TiO 2 –ZnO multilayers in tailoring refractive index profiles, offering promising applications in advanced optical coatings such as UV-selective mirrors, antireflective layers, and photonic devices operating in the ultraviolet regime.