Characterization of Periodic Ag/Al2O3/SiO2/Si Multilayer Structures by Spectroscopic Ellipsometry

Abstract

In this work, multilayer structures based on consecutive thin films of silver (Ag) and alumina (Al₂O₃) were grown on silicon substrates by RF reactive sputtering technique. With a layer period containing consecutive Ag and Al₂O₃ films, the number of these periods was varied to introduce their effects on the optical characteristics of the fabricated structures. The spectroscopic ellipsometry was carried out on these structures to determine the ellipsometric parameters (amplitude ratio Ψ and phase shift difference Δ) as functions of incident light wavelength for three different incidence angles (60°, 70°, and 80°). Results showed that the larger number of periods resulted in a higher sensitivity to the incidence angle by the multilayer structure, which is very crucial for practical applications such as optical filters and photonic sensors as the thickness and structure of these layers are controlled to achieve certain optical response within a desired wavelength ranges.