Template-Assisted Self-Assembly of Colloidal Silicon Nanoparticles for All-Dielectric Nanoantenna

摘要

A solution-based bottom-up process to produce one- and two-dimensional arrays of densely packed spherical nanoparticles (NPs) of crystalline silicon (Si), having the lowest order Mie resonance in the visible range, is developed. First, an agglomeration-free solution of Si NPs with a narrow size distribution is prepared. By using grooves fabricated on the surface of a polymer as a template, arrays of Si NPs with different shapes are formed by a template-assisted self-assembly method, and then they are transferred to an arbitrary substrate. To demonstrate proper formation of Si NP arrays, polarization-resolved scattering spectra are measured for different size linear arrays, i.e., a monomer to a pentamer, of Si NPs placed on a silica substrate. The observed spectra are well-reproduced by the numerical simulations. When the polarization direction of incident light is parallel to the array axis, the scattering spectra are strongly modified from that of a Si NP monomer due to near-field coupling of the electric dipole (ED) modes. In a Si NP tetramer, the peak of the ED mode overlaps with that of the magnetic dipole (MD) mode and strong forward scattering is observed at the MD peak wavelength due to the Kerker effect.