Light scattering from core-shell nano-structures : structural coloration

Abstract

In this work, we produced kilometer-long semiconducting cylindrical nanostructures by using a top-to-bottom nano-fabrication technique which was recently developed in our research group. Comparison of commonly used methods of producing nano-structures such as electrospinning and nano-imprint lithography versus iterative thermal size reduction (ISR) is done in terms of uniformity, geometry control, multi-material compatibility, yield and device integrability. While the others cannot fulfil all requirements, ISR shows impressive results in all aspects. From very beginning to end, all steps of production and characterization of nano-wires produced by ISR, the design, chalcogenide glass production, preform preparation, fiber drawing, iterative size reduction, chemical etching and imaging are explained in details. In addition, production and characterization of nanospheres by in-fiber fluid instability which is based on Plateau-Rayleigh instability is also demonstrated. Theoretical study on scattering from small particles, Mie scattering, which is one of the mechanisms for structural coloration together with thin film interference, multilayer interference, diffraction grating and photonic crystals is done. Structural coloration due to scattering from small particles is simulated using Finite Domain Time Difference (FDTD) method and compared with theoretical results estimated for nano-wire and nano-sphere cases. Results are confirmed with observation of structural coloration by taking dark field optical microscopy images of the final products of ISR and in-fiber fluid instability processes