Self-assembly of Si-based particles for infrared-active metamaterials Megan Parker 1 , Lucien Roach 1 , Raul Barbosa 2 , Maria L. De Marco 1 , Alexander Castro-Grijalba 1 , Brian A. Korgel 2 , Sabrina Lacomme 3 , Vasyl G. Kravets 4 , Alexander N. Grigorenko 4 , Phillippe Barois 5 , Virginie Ponsinet 5 , Glenna L. Drisko 1 1 CNRS, Université de Bordeaux, Bordeaux INP, Institut de Chimie de la Matière Condensée de Bordeaux, UMR 5026, 33600 Pessac (France), 2 McKetta Dpartment of Chemical Engineering, The University of Texas at Austin, 200 E Dean Keeton St, Austin TX 78712 (USA), 3 CNRS, INSERM, Bordeaux Imaging Center, UMS 3420, US 4, 33000 Bordeaux (France), 4 Department of Physics and Astronomy, The University of Manchester, Manchester M13 9PL (U.K.), 5 CNRS, Université de Bordeaux, Bordeaux INP, Centre de Recherche Paul Pascal (CRPP), UMR 5031, 33600 Pessac (France) Core-shell particles were designed to achieve optical metamaterials with forward light scattering properties in infrared frequencies. Forward light scattering, referring to the light transmitted forward with respect to the incidence angle, with no reflection in the backward direction, is a property useful in light harvesting and anti- reflective screens. 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 . This was achieved by combining a silicon coordination complex with trisilane in supercritical hexane. 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, cyclohexasilane, combined with the same coordination complex. Core and shell dimensions were controlled through precursor stoichiometry and absolute concentration. The electric and magnetic multipoles were characterized using a custom-built static light scattering spectrometer. 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. Particles were deposited onto an air-water interface into a close- packed monolayer. Initial characterization of the films show resonances at near-infrared and infrared frequencies. The optical properties of 2D assemblies of scatterers will be further experimentally studied using ellipsometry, and the results will be compared to simulations. References 1. De Marco, M. L.; Jiang, T.; Fang, J.; Lacomme, S.; Zheng, Y.; Baron, A.; Korgel, B. A.; Barois, P.; Drisko, G. L.; Aymonier, C. Broadband Forward Light Scattering by Architectural Design of Core–Shell Silicon Particles. Adv. Funct. Mater. 2021, 31 (26), 2100915. https://doi.org/10.1002/adfm.202100915.
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