Surface plasmon resonances in the absorption spectra of nanocrystalline cupric oxide

TL;DR

This paper investigates the optical absorption spectra of nanocrystalline cupric oxide, revealing surface plasmon resonances caused by metallic-like nanoscale droplets, with a model explaining temperature-dependent spectral features.

Contribution

It introduces a minimal model linking spectral shifts and features to surface plasmon resonances in nanocrystalline CuO, supported by effective medium theory.

Findings

Spectral weight red-shift in nanocrystalline CuO compared to single crystals.

Observation of temperature-dependent 'peak-dip-hump' feature near 1.3-1.6 eV.

Effective medium theory successfully describes the experimental spectra.

Abstract

Optical absorption spectra of nanocrystalline cupric oxide CuO samples, obtained using the converging spherical shock wave procedure, reveal significant spectral weight red-shift as compared with spectra of single crystalline CuO samples. In addition, some of these samples manifest the remarkable temperature-dependent "peak-dip-hump" feature near 1.3-1.6 eV. The minimal model suggested to explain both effects implies the nanoceramic CuO to be a system of two species of identical metallic-like droplets with volume fractions p1 >> p2 and damping parameters gamma1 >> gamma2, respectively, dispersed in an effective insulating matrix. In other words, both effects are assigned to the surface plasmon (Mie) resonances due to a small volume fraction of metallic-like nanoscale droplets with Drude optical response embedded in the bare insulating medium. Simple effective medium theory is shown to provide the reasonable description of the experimental spectra.