Self-Assembled Silicon@Silica Metasurfaces with High-Quality Resonances in the Infrared.

2D assemblies of resonant dielectric particles constitute promising materials for the next generation of photonic devices, thanks to their low optical losses and intense electromagnetic response. However, bottom-up synthesis methods present many difficulties when targeting metasurface applications, particularly due to the high degree of positional disorder and the size dispersion of the resonant particles. This work presents the fabrication of core-shell silicon@silica particles with multipolar resonances in the visible and near-infrared. These resonant particles are then assembled at an air-water interface into a semi-ordered array with islands of crystallinity. The assembly is deposited on quartz and the optical properties are characterized with ellipsometry and optical microscopy. The effective medium of this material appears to display a magnetic resonance with a high-quality factor at ≈945 nm, as demonstrated by a Lorentzian resonance in the permeability. Thus, this is the first bottom-up synthesis of silicon particle assemblies known to generate optical magnetism, giving promise for the scalable production of high-performance metasurfaces, in spite of the imperfections associated with bottom-up fabrication.