Unveiling the optical properties of a metamaterial synthesized by electron-beam-induced deposition

TL;DR

This paper investigates the optical properties of electron-beam-induced deposited metamaterials, focusing on their effective permittivity and how it varies with gold nanocrystal density, revealing limitations of traditional models.

Contribution

It provides experimental measurements of the permittivity of gold-containing deposits and highlights the inadequacy of the Maxwell-Garnett model for these materials.

Findings

Permittivity depends systematically on gold nanocrystal density.

Maxwell-Garnett approach does not adequately describe the optical response.

Spectroscopic measurements reveal complex light-matter interactions.

Abstract

The direct writing using a focused electron beam allows for fabricating truly three-dimensional structures of sub-wavelength dimensions in the visible spectral regime. The resulting sophisticated geometries are perfectly suited for studying light-matter interaction at the nanoscale. Their overall optical response will strongly depend not only on geometry but also on the optical properties of the deposited material. In case of the typically used metal-organic precursors, the deposits show a substructure of metallic nanocrystals embedded in a carbonaceous matrix. Since gold-containing precursor media are especially interesting for optical applications, we experimentally determine the effective permittivity of such an effective material. Our experiment is based on spectroscopic measurements of planar deposits. The retrieved permittivity shows a systematic dependence on the gold particle density and cannot be sufficiently described using the common Maxwell-Garnett approach for effective medium.