Spectroscopic ellipsometry on metal and metal-oxide multilayer hybrid plasmonic nanostructures

The effective medium approximation is used to determine the optical constants of novel silver (Ag)/indium-tin oxide (ITO) multilayer nanopillar structures within the 300-800 nm wavelength range. The structures are modeled as inclusions in air with the pillar volume fraction at 42.4%, agreeing with SEM images of the sample. The simulated reflection intensity of the nanopillars is much less than that of the planar reference sample and is a result of the small difference between the refractive index of the top effective medium layer and that of air. Furthermore, the minimum in the reflection at around 450 nm in the nanostructured sample is evidence of surface plasmon enhancement, indicating suitability for plasmonic applications. The simulated Brewster angle decreases in the pillar region, which is an indication of smaller effective refractive index.