Fabrication of Monodisperse Colloids of Resonant Spherical Silicon Nanoparticles: Applications in Optical Trapping and Printing

We present a new method for making monodisperse highly spherical polycrystalline silicon (Si) nanoparticles dispersed in solution and a method for trapping, moving, and printing these nanoparticles on a substrate. Spherical Si nanoparticles with low dispersion in size (<3.5%) and diameter of 130 and 210 nm were fabricated using combined hole-mask colloidal lithography and laser-induced transfer. The particles are highly crystalline and possess electric and magnetic dipole resonances in the visible spectrum varying with the diameter. They could be trapped in 2D against a substrate using an optical tweezer and then printed onto the substrate by means of radiation pressure. The proposed method paves the way for the use of optical forces for assembling complex resonant dielectric nanostructures with engineered optical properties.