Self-assembly of Si-based particles for infrared-active metamaterials
Résumé
The synthesis and self-assembly of Si@SiOxNy core-shell particles, optically active at infrared wavelengths is reported. In a previous work we demonstrated that similar particles with reduced size (~350 nm) more efficiently supported forward light scattering, and over a broader region of the visible spectrum, than pure silicon particles.1 Here, the scattering frequencies are shifted to the infrared, with the synthesis of larger particles (~540 nm) obtained from the use of a different silane precursor.2 Individual particles were produced by decomposing a Si coordination complex alongside cyclohexasilane, under supercritical conditions. The bottom-up approach employed here leads to particles fulfilling the requirements for efficient light scattering: being smaller than the wavelength of incident light and large enough to support Mie resonances at optical frequencies and being monodisperse in size. The synthesis of the core@shell particles only produces a relatively small amount of material (~5 mg per batch) which heavily restricts the self-assembly techniques that can be employed to prepare a monolayer. The strategy ultimately pursued here was interfacial self-assembly within a restricted area. Particles were deposited onto an air-water interface from a 2:1 ethanol:butanol suspension and then transferred to a hydrophilic substrate. The prepared films are not completely close-packed and have a degree of disorder (c.f. a HCP monolayer). The optical properties of 2D assemblies of scatterers are studied using ellipsometry, and the results are compared to simulations.
Domaines
MatériauxOrigine | Fichiers produits par l'(les) auteur(s) |
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