(456b) Atomic Layer Deposition Of Optically Active Zno And TiO2 Nanothick Films On Particles

The scattering, absorbance and transmittance of colloidal dispersions of dielectric core-shell nanoparticles fabricated by atomic layer deposition (ALD) is evaluated in this work. The optical dispersion of dielectric nanoparticles, specifically ZnO and TiO₂, increases in importance as the wavelength approaches the ultraviolet (UV) spectrum. This is an inherent issue in resolving the effectiveness of inorganic sunscreen particles under incident solar irradiation. Rigorous experimental design techniques are employed to understand the optical dispersion of nanothick ALD films of ZnO and TiO₂, above and below the band gap, on 2-D surfaces using Spectroscopic Ellipsometry. Particle-ALD is then utilized to deposit these dielectric films on spherical SiO₂ particles to create novel 3-D nanocomposite structures for dispersion in liquids. Mie Scattering theory is used to model the optical properties of the nanocomposite particle suspensions. Theory is compared to experiment using UV-VIS Spectrophotometry. The optimal coating thickness to maximize UV blocking potential at given solids loadings is discussed.