Large-Scale and Low-Cost Fabrication of Silicon Mie Resonators
Résumé
High index dielectric nanoparticles have been proposed for many different applications. However, widespread utilization in practice also requires large-scale production methods for crystalline silicon nanoparticles, with engineered optical properties in a low-cost manner. Here, we demonstrate a facile, low-cost, and large-scale fabrication method of crystalline silicon colloidal Mie resonators in water, using a blender. The obtained nanoparticles are polydisperse with an almost spherical shape and the diameters controlled in the range 100−200 nm by a centrifugation process. Then the size distribution of silicon nanoparticles enables broad extinction from UV to near-infrared, confirmed by Mie theory when considering the size distribution in the calculations. Thanks to photolithographic and drop-cast deposition techniques to locate the position on a substrate of the colloidal nanoparticles, we experimentally demonstrate that the individual silicon nanoresonators show strong electric and magnetic Mie resonances in the visible range. E fficient control of the visible light at the nanoscale is a key issue for integrated photonics devices. Surface plasmon resonance (SPR) 1 excited in noble metal is recognized as a promising way to control light at the nanoscale. Such a unique optical property has been widely used for many different applications such as surface-enhanced Raman scattering, 2 biological sensing, 3 photovoltaic devices, 4 and metamaterials. 5 However, metals suffer from non-negligible intrinsic Ohmic losses, limiting the field of potential application. 6 Contrary to plasmon-based light confinement at the nanoscale, high-refractive index dielectric nanoparticles offer a novel paradigm for light enhancement and manipulation at the nanoscale. Indeed, excitation of Mie resonances in such nanoparticles results in strong light scattering and an optical near-field enhancement, along with low Ohmic losses and thermal stability. However, silicon nanoparticles show multiple magnetic and electric resonances in the visible and the near-infrared spectral regions. 7−9 Then the overlap between their electric and magnetic resonance modes provides Mie resonators unique light scattering properties like Kerker-type high directional scattering. 9,10 All these optical properties allow silicon nanoparticles to be used in many applications like nonlinear optics, 11−13 Raman scattering enhancement, 14 directional optical sorting, 15 color printing, 16−18 ultrafast optical switching, 19 wavefront manipulation, 20 optical heating (with submicronic particles), 21 and many others. The wide range of applications already proposed based on Mie resonators underlines the need for flexible, low-cost fabrication methods. Electron beam lithography associated with chemical etching 22 has been demonstrated as an efficient method to fabricate nanoparticles of different shapes with very sharp edges. A modified version of hole-mask colloidal lithography associated with a chemical etching of the substrate is an original technique that leads to silicon nanostructures well adapted to large area fabrication. 23 The major drawback of such methods is its very high cost. Moreover, they do not allow the fabrication of spherical-shaped colloidal nanoparticles. Recently, femtosecond laser printing 24,25 has been introduced by Chichkov's team. They demonstrate the possibility of inducing spherical crystalline nanoparticles of silicon. More