Spectral response of nanocrystalline ZnO films embedded with Au nanoparticles

Abstract

The optical response of a two-phase composite consisting of Au nanoparticles (AuNPs) in a nanocrystalline ZnO thin film matrix has been systematically studied and analyzed by the Bergman-Milton spectral density formalism. The real and imaginary parts of the effective dielectric function exhibited anomalous dispersion and absorption, respectively, at the characteristic localized surface plasmon resonance (LSPR) wavelength. A multilayer structure consisting of two AuNP-ZnO composite films separated by a thin ZnO film displayed a twofold increase in the absorption at LSPR (with negligible change in FWHM), which is attributed to the increase in the number density of the AuNPs resulting from the nanocrystalline nature of the ZnO film. The results have been used to correlate the spectral density function to the morphology of AuNPs in a ZnO matrix.

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“…36 Moreover, the presence of these high-order oscillatory modes red shifts the LSPR resonance absorption peaks. 37 For metal NSs with radii much smaller than the wavelength of the incident light, the electromagnetic field exerted by the incident light can be said to be uniform throughout the metal NS, so that isolated individual metal NS do not undergo multi-order resonance. Moreover, some high-order resonance modes are prohibited for symmetric metal NS excited by linearly polarized light at normal incidence.…”