Atomic layer deposition for hafnium oxide-based meta-optics in the ultraviolet spectral range

Hafnium oxide (HfO$_2$) is a high-index dielectric material of growing importance for optical coatings and meta-optical components operating from the ultraviolet (UV) to the visible spectral range. Its large bandgap, chemical stability, and compatibility with established semiconductor processes make it particularly attractive for applications requiring low absorption and precise thickness control. In this work, we investigate the optical material properties of HfO$_2$ thin films deposited by plasma-enhanced atomic layer deposition (PEALD). The complex refractive index is experimentally determined over a broad spectral range extending from the vacuum ultraviolet (140 nm) to the visible (600 nm) by combining spectroscopic ellipsometry, spectrophotometry, and infrared ellipsometry. A comprehensive dispersion model is employed to extract consistent optical constants and thickness values. The results highlight the suitability of PEALD-grown HfO$_2$ films for advanced optical and meta-optical applications.