Ellipsometry of hybrid noble metal-dielectric nanostructures

Abstract

Angular ellipsometric measurements of thin Ag, Cu films covered by HfO 2 protective layer were performed. The ellipsometric parameters ψ and ∆ were measured in θ = 43°...85° light incidence angle range, where ψ is the azimuth of restored linear polarization, ∆ is the phase shift between p- and s-components of reflected light. For comparison, thin Au film (traditional sensor for surface plasmon resonance (SPR)) was examined as well. The curve ∆(θ) for all the samples investigated falls down with increasing angle of light incidence, while ψ(θ) changes relatively weakly. It has been ascertained that the increase in the thickness of HfO 2 layer affects the tan(ψ) value, while tan(ψ) deviation is mainly determined by the type of metallic film. With the growth of HfO 2 layer, the minimum position of tan(ψ) shifts to smaller angles. From these angular dependences, one could choose the appropriate SPR-compatible structure due to maximal deviation of tan(ψ). To optimize layer thickness for a high SPR-response, spectral measurements and additional calculations are required.

Keywords

• ellipsometry
• thin film
• noble metals
• surface plasmon resonance
• hafnium oxide