Self-assembly of plasmonic/excitonic silicon nanocrystals into photonic crystals
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lasmonics, Photonics, and Metamaterials Research Letter
Self-assembly of plasmonic/excitonic silicon nanocrystals into photonic crystals Jihua Yang, Nicolaas J. Kramer, Christopher J. Hogan Jr., and Uwe R. Kortshagen, Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA Address all correspondence to Uwe R. Kortshagen at [email protected] (Received 1 October 2015; accepted 30 November 2015)
Abstract In this work, photonic crystals of plasmonic/excitonic semiconductor nanocrystals (NCs) were assembled from non-thermal plasma-synthesized boron (B)-doped silicon (Si) NCs. The photonic crystals form an inverse opal structure with larger refractive index than the conventional crystals made from silica nanoparticles and are aimed at controlling light propagation via excitonic and plasmonic absorption of the B-doped Si NC as well as the photonic band gap of the photonic crystal. Furthermore, we demonstrate self-assembly of mesoscopic photonic crystal particles consisting of B-doped Si NCs with well-defined inverse opal structure via simple aerosol processing.
The controlled assembly of functional nanoparticles can lead to nanostructures with tailored electromagnetic propagation. For example, integrating metallic plasmonic nanoparticles such as nanospheres and nanorods into architectures with well-designed geometries and sizes can control the plasmonic interaction of particles, leading to Fano resonance-based transparency windows.[1] Notably, photonic crystals, i.e., ordered arrays with different refractive indices and a periodicity of the order of light wavelength, prevent propagation of light in certain ranges of energy, termed the photonic band gap. The position of the photonic band gap can be controlled by adjusting the periodicity and effective refractive index. Photonic crystals composed of silica nanoparticles have been widely studied with polystyrene latex (PSL) spheres as templates.[2,3] The concept of photonic crystals can be extended to mesoscale particles, which would be of interest as active material in optical metafluids,[4–7] in specialized paints with tailored optical properties, or even aerosols with designed optical characteristics. Aerosol-based assembly of mesoporous particles out of silica and titania nanoparticles has been successful, as is reported in Refs. 8,9. In these studies, a mixture of colloidal nanoparticles and PSL template spheres in water was atomized and the surface tension of the evaporating solvent caused the hexagonally closely packed assembly of the PSL spheres with the nanoparticles filling the voids in between.[8–11] Thermal annealing of these particles removed the PSL spheres and yielded photonic crystal mesoparticles. The goal of this work is to integrate multifunctional plasmonic/excitonic semiconductor nanocrystals (NCs) into photonic crystal thin films and mesoparticles. Such structure should combine the photonic band gap of the photonic crystal
with the excitonic behavior as well as the plasmonic response of the semiconductor NCs. We here rep
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