Influence of surface roughness on the optical properties of plasmonic nanoparticles

TL;DR

This study examines how surface roughness affects the optical properties of plasmonic nanoparticles, finding minimal impact on plasmon resonance features, supported by experiments and boundary element method simulations.

Contribution

It provides new insights into the limited influence of surface roughness on plasmonic nanoparticle optical properties, using a perturbation approach and motional narrowing explanation.

Findings

Surface roughness has a surprisingly small effect on plasmon peak position and width.

Experimental results align with boundary element method simulations.

Surface roughness is not a major obstacle in large nanoparticle arrays for metamaterials.

Abstract

For plasmonic nanoparticles, we investigate the influence of surface roughness inherent to top-down fabrication on the optical properties, and find that it has a surprisingly small influence on the position and width of the plasmon peaks. Our experimental observation is supported by simulations based on the boundary element method approach. Using a perturbation approach, suitable for metallic nanoparticles with a moderate degree of surface roughness, we demonstrate that the reason for this lies in motional narrowing where the plasmon averages over the random height fluctuations. Surface roughness in large arrays of identical nanoparticles, such as encountered in the context of metamaterials, is thus expected to not constitute a major roadblock.