CuS NanoDisk Films as Plasmonic Metamaterials

Abstract

Plasmonic materials are widely used for developing applications in nonlinear and ultrafast optics, photochemistry, and confinement and manipulation of electromagnetic fields. There is a strong drive in the search for alternative to traditional metals plasmonic materials, with lower losses and controlable optical properties. In this work, an investigation of Copper Sulphide (CuS) nanodisks and their films are presented which is p-type plasmonic material and exhibit interesting plasmonic behaviour in the near-infrared spectral range. CuS nanodisks are chemically synthesised and deposited using chemical functionalization or electrophoresis to obtain highly homogeneous, smooth films of monolayer and multilayer thickness on glass or conductive substrates, respectively. I investigate the optical behavior of the films using ellipsometry and reflection/transmission spectroscopy to extract the optical permittivity of the nanodisk film effective medium. Surface plasmon polariton excitation was studied both experimentally and theoretically. I further characterize the CuS thin film properties using pump-probe techniques to investigate the transient hot-hole dynamics in the CuS. Because of the lower free-carrier concentration, it was shown CuS exhibits a faster carrier relaxation than in traditional plasmonic materials. Further, excitation of coherent optical phonon modes in CuS lattice was also demonstrated, revealing for the first time coherent lattice dynamics in plasmonic materials. A novel chemical technique was developed to tune the permittivity and, therefore, localised surface plasmon spectral position in CuS nanodisks by doping them with Zinc. This allowed us to achieve a localised surface plasmon tuneable in 1240-1750 nm spectral range. Copper sulfide as an unusual p-type plasmonic material has unique properties for developing near-infrared plasmonic nanostructures and devices with faster nonlinear optical response and tuneability not possible in traditional metal-based plasmonic materials.

Date of Award	1 Jun 2022
Original language	English
Awarding Institution	King's College London
Supervisor	Anatoly Zayats (Supervisor) & Mark Green (Supervisor)