engleski

Film - coupled silver nanoparticles on flat and periodically corrugated aluminium substrates

The strong scattering of light by noble metal nanoparticles has, since ancient times, been utilized in various ways, from Roman stained glass to modern day hCG pregnancy tests. At optical frequencies, both the "lightning rod effect" associated with nanometer geometric features and the excitation of collective charge oscillations known as localized surface plasmons (LSPs) contribute to the formation of strong and highly localized electric field "hotspots" at the nanoparticle surface. Understanding the "hotspot" formation mechanism and its attributes such as resonant wavelength, excitation efficiency or spatial confinement, as well asmastering the technology to efficiently produce LSP systems with desired properties, has been at the focus of plasmonics and nanooptics in the past decade and motivated by the perspective of producing a new generation of ultrasensitive spectroscopic sensors or controlling the photon generation by quantum emitters. A significant recent development has been realized by the use of the layer-by-layer polyelectrolite deposition technique, providing cheap means to produce dielectric layers the thickness of which can be controlled with subnanometer precision. Here we report on a comprehensive study of optical properties of silver nanospheres or nanocubes separated from a flat or periodically corrugated aluminium substrate by a few nanometer thick layer of oxide and several polyelectrolite layers. Combining theoretical methods based on the mixed representation of the Dyadic Green function for the electric field, numerical simulations employing the finite element method, various colloidal synthesis protocols for silver nanoparticle generation, holographic generation of periodically corrugated surfaces, electron beam deposition of aluminium films, layer-by-layer polyelectrolite deposition, spectrophotometry, spectroscopic ellipsometry, Raman spectroscopy and atomic force microscopy, we investigate the properties of surface plasmon polaritons of the aluminum surface [4] and their role in the formation of LSPs highly localized in tiny gaps between the nanoparticle and aluminium substrate.

silver nanoparticles ; layer-by-layer deposition ; light scattering

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