Quantitative modelling of the surface plasmon resonances of metal nanoclusters sandwiched between dielectric layers: the influence of nanocluster size, shape and organization

Abstract

The effects of size, shape and organization on the surface plasmon resonances of Ag nanoclusters sandwiched between Si(3)N(4) layers are studied by transmission electron microscopy and anisotropic spectroscopic ellipsometry. We present an easy-to-handle model that quantitatively links the nanostructure and optical response of the films, which are considered as dielectric/metal:dielectric/dielectric trilayers, with the central nanocomposite layer being an effective medium whose optical properties are described by an anisotropic dielectric tensor. The components of this tensor are calculated using a generalization of the Yamaguchi theory taking into account the real organization, size and shape distributions of ellipsoidal nanoclusters, whose electronic properties are assumed to reflect shape-dependent finite size effects. Using this model, it is shown that the optical response of the films in the visible range is dominated by the excitation of the surface plasmon resonance of the clusters along their in-plane long axis, while no surface plasmon resonance resulting from an excitation along their in-plane short axis can be observed due to damping effects. Moreover, the spectral position of this resonance appears to be mainly affected by the average shape of the clusters, and weakly by their size, their shape distribution and the electromagnetic interaction between them.

Advanced optical effective medium modeling for a single layer of polydisperse ellipsoidal nanoparticles embedded in a homogeneous dielectric medium: Surface plasmon resonances

“…Let us moreover note that, if we assume a monodisperse system of spheroidal NPs (a = b and thus α a = α b ), Eq. (31) leads to the Yamaguchi formulas 36,38 written to match the case of NPs embedded in a homogeneous dielectric medium 51,52 (i.e., with no image dipole field contributions) and with an isotropic in-plane organization.…”

“…The size, shape anisotropy and related distributions clearly depend on the nature of the dielectric material: NPs present more anisotropic shapes when embedded in a Si 3 N 4 medium than in a BN medium. 48 These trends were quantified by digital analysis of the TEM images, 48,51 thus providing the average interparticle distance , the distributions of the in-plane effective diameter D, the in-plane axis ratio b/a and the height-to-effective diameter ratio H/D of the NPs. As shown in Figs Table I, together with the values of , and the average in-plane effective diameter D and hwhm w of the D distribution used in the following optical calculations for both films.…”

“…To our knowledge, little has been reported about easily implementable effective medium models suitable for the case of single layers of polydisperse ellipsoidal NPs, with two of their principal axes being in the layer's plane. 51 Especially, the influence of a polydisperse height distribution of the NPs, which may be correlated to their in-plane effective size and in-plane projected shape in real systems, has not been examined so far.…”

Optical reflectivity of a disordered monolayer of highly scattering particles: coherent scattering model versus experiment

“…The optical reflectivity of disordered monolayers of particles has been of interest for many years now [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Particular attention was paid in the past to the case of monolayers of small metallic particles whose size is much smaller than the incident wavelength adsorbed on a flat surface (see, for instance, [2][3][4][5][6][7][8][9][10][11]).…”

Plasma-Assisted Deposition of Au/SiO2 Multi-layers as Surface Plasmon Resonance-Based Red-Colored Coatings

“…7 shows a red shift of the plasmon resonance by increasing the metal surface area coverage on each layer and reducing the SiO 2 interlayer thickness. This is due to a deviation from the Mie plasmon resonance as a result of interparticle interaction and coupling in the SPR [37][38][39]. Taking into account that the SiO 2 interlayer is thick enough to avoid the SPR coupling between the Au layers, multi-layers are a valid solution to the production of strong colored coatings in which the color of the coating is virtually independent from the thickness of the film.…”