Diffuse Surface Scattering and Quantum Size Effects in the Surface Plasmon Resonances of Low Carrier Density Nanocrystals

TL;DR

This paper theoretically explores how diffuse surface scattering and quantum size effects influence the localized surface plasmon resonances in low carrier density nanocrystals, revealing size-dependent oscillatory behaviors.

Contribution

It introduces a theoretical model combining diffuse surface scattering and quantum size effects to explain LSPR evolution in doped semiconductor nanocrystals.

Findings

QSE causes a blueshift in LSPR energy.

Diffuse surface scattering induces oscillatory-damped size dependence.

LSPR behavior strongly depends on the relation between size and characteristic lengths.

Abstract

The detailed understanding of the physical parameters that determine Localized Surface Plasmon Resonances (LSPRs) is essential to develop new applications for plasmonics. A relatively new area of research has been opened by the identification of LSPRs in low carrier density systems obtained by doping semiconductor quantum dots. We investigate theoretically how diffuse surface scattering of electrons in combination with the effect of quantization due to size (QSE) impact the evolution of the LSPRs with the size of these nanosystems. Two key parameters are the length $R_0$ giving the strength of the QSE and the velocity $\beta_T$ of the electronic excitations entering in the length scale for diffuse surface scattering. While the QSE itself only produces a blueshift in energy of the LSPRs, the diffuse surface scattering mechanism gives to both energy and linewidth an oscillatory-damped behavior as a function of size, with characteristic lengths that depend on material parameters. Thus, the evolution of the LSPRs with size at the nanometer scale is very dependent on the relation of size to these lengths, which we illustrate with several examples. The variety of behaviors we find could be useful for designing plasmonic devices based on doped semiconductor nano structures having desired properties.