Diffuse Surface Scattering in the Plasmonic Resonances of Ultra-Low Electron Density Nanospheres

TL;DR

This paper investigates how diffuse surface scattering influences the plasmonic resonances in ultra-low electron density nanospheres, revealing it as a dominant factor over spill-out effects, with results aligning with recent experiments.

Contribution

It introduces a theoretical framework combining diffuse surface scattering and quantum size effects to explain plasmonic behavior in low-density nanospheres.

Findings

Diffuse scattering causes oscillations in LSPR position and width for large particles.

Smaller particles exhibit a blueshift and increased resonance width.

Diffuse scattering is more significant than spill-out in these systems.

Abstract

Localized surface plasmon resonances (LSPRs) have recently been identified in extremely diluted electron systems obtained by doping semiconductor quantum dots. Here we investigate the role that different surface effects, namely electronic spill-out and diffuse surface scattering, play in the optical properties of these ultra-low electron density nanosystems. Diffuse scattering originates from imperfections or roughness at a microscopic scale on the surface. Using an electromagnetic theory that describes this mechanism in conjunction with a dielectric function including the quantum size effect, we find that the LSPRs show an oscillatory behavior both in position and width for large particles and a strong blueshift in energy and an increased width for smaller radii, consistent with recent experimental results for photodoped ZnO nanocrystals. We thus show that the commonly ignored process of diffuse surface scattering is a more important mechanism affecting the plasmonic properties of ultra-low electron density nanoparticles than the spill-out effect.