Negative permittivity and permeability of gold nanorods metamaterials in UV- Vis region

TL;DR

This study experimentally demonstrates negative permittivity and permeability in gold nanorods grown on substrates, a phenomenon previously only predicted by simulations for simple structures, opening new avenues for optical device applications.

Contribution

First experimental observation of negative optical parameters in gold nanorods, confirming theoretical predictions and expanding the understanding of simple metamaterials.

Findings

Gold nanorods exhibit negative permittivity and permeability in UV-Vis region.

Negative optical parameters were achieved in simple nanostructures, not just complex artificial ones.

Sample size and thickness influence the negative optical behavior.

Abstract

In this article, we report the growth of gold nanorods on glass substrates and copper nanoparticle thin films by cylindrical direct current magnetron sputtering (CDCMS) at room temperature. The grown gold nanorods have short lengths of < 20nm and show negative optical parameters in UV-Vis region. So far negative permittivity and permeability were only shown for complex artificial structures. In a case of simple structures like gold nanorods, the negative optical parameters were only predicted by simulation methods and considering ideal structures and they were not yet reported by experimental groups, who has grown or synthesis gold nanorods by physical or chemical methods. The small size of gold nanorods and thickness of our samples compare to other experimental groups could be the reason of negative permittivity and permeability in our case. Low loss metamaterials with simultaneously negative permittivity and permeability are desired for practical applications in many optical devices such as optical switching, waveguides, modulators, and plasmonic antenna arrays. The optical properties of the grown gold nanorods were defined by ultraviolet- visible (UV-Vis) spectroscopy and their quality was assessed through multi-technique characterization using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and energy dispersed X-ray (EDX).