The characterization of Al2O3 and TiO2 antireflection coatings with a novel X-Ray reflectivity method and other experimental techniques

Al
₂
O
₃
/TiO
₂
/Al
₂
O
₃
multilayer antireflection stacks used for broadband antireflection coatings and TiO
₂
and Al
₂
O
₃
single layers were characterized by a novel combination of an X-ray reflectivity layer extraction algorithm, X-ray reflectivity simulations, spectroscopic ellipsometry, broadband optical reflectance, glancing incidence X-ray diffraction and transmission electron microscopy. Single-layer TiO
₂
and Al
₂
O
₃
antireflection coatings were also measured by glancing incidence small angle X-ray scattering. Layer thicknesses and surface and interface roughnesses with a few Å precision, densities normalized to bulk densities with less than one percent uncertainty, and differences in pore-induced scattering were assessed. These parameters are key to understanding the role of deposition and processing conditions on the performance of broadband antireflection coatings. Additionally, the effect of air annealing at 400 °C for 10 min and 40 min on the structural and optical properties of single-layer TiO
₂
and Al
₂
O
₃
antireflection coatings was also revealed.