Directional light scattering in Mie-resonant Si particles with ultra-thin Au shells

In the present work, we present Au-decorated Si core-shell (Si@Au) particles, which show enhanced forward scattering compared to Mie-resonant Si particles alone. TEM images show the synthesized Si particles with size dispersity and the Au-decorated Si particles. The UV-Vis-NIR spectra and EDX spectroscopy further confirm the synthesis of Si@Au particles. The Si core sizes are between 100 – 200 nm, while the Au particles with ∼4 nm diameter form the shell. Electron energy-loss spectroscopy (EELS) mapping and optical single-particle backward-scattering spectroscopy confirm the resonant behavior of the core-shell particles. These observations were supported by T-matrix simulations and Mie-theory calculations of the scattering spectra, which show that Si and Si@Au particles demonstrate a dampened magnetic dipole resonance for smaller sizes (100 – 130 nm) and an enhanced magnetic dipole resonance for larger Si particle sizes (150 – 200 nm).