The Fabrication And Properties Of 3D Micro/Nano Plasmonic Structures

The Surface plasmon polarizations(SPPs)and the localized surface plasmons(LSPs) occur when the plasmonic structures are excited by light.These SPPs or LSPs can propagate at the metal surface or provide a strong near-field enhancement of electromagnetic wave.Because of these fascinating properties of LSPs and SPPs,plasmonic structures show great potential in the application of condensed matter physics,materials chemistry,and biomedical science.Among all kinds of plasmonic structures,3D plasmonic nano-structures play important roles in ultra-sensitive bio-molecules detection,high-efficient metamaterials,and even in quantum devices for their advantages such as far more controllable degrees of freedom and higher integration level compared to their 2D counterparts.For the reasons mentioned above,the research progress in preparation and applications of 3D plasmonic structures,especially 3D nanogaps and 3D origami structures,have became a‘hot-spot’in the past decade.This paper focuses on the preparation of 3D structures by new processing methods,and their properties and potential applications in the light regulation.Firstly,two methods have been developed for the fabrication of plasmonic nanogaps in order to circumvent the limitation of traditional micro-fabrication technologies:1.Suspend nanogaps can be prepared by stress induced crack method;2.A glancing angle deposition method is introduced for the fabrication of sub-5 nm metallic gaps.Both methods are suitable for the controllable configuration and rapid fabrication of 3D sub-10 nm plasmonic gaps.Moreover,the fabricated nanogaps can be applied to surface enhanced Raman scattering(SERS)substrates.The nanogaps demonstrate a SERS enhancement factor of 10~8,capable of single molecule detection.Surface enhanced fluorescence(SEF)devices can also be designed by shadow defined nanogaps.Secondly,a novel focused ion beam(FIB)induced bending method is proposed for the rapid preparation of 3D nano-structures.The radius of the bended structure(down to 175nm)can be continuously tuned by changing the energy and the dose of FIB irradiation.Most importantly,this method is compatible with the FIB induced fold method,which means the diversity of 3D origami configuration is significantly improved.This method lays a foundation for the design and fabrication of 3D devices.Finally,two types of metamaterials are designed and experimentally proven:1.A polarization insensitive metamaterial with multiple high-quality(high-Q)resonances is designed based on the fano-type resonance in the vertically split ring resonator.A Q-factor of 98 can be obtained at mid-infrared frequency.2.FIB induced bending method is also suitable for the fabrication of unidirectional reflectionless metasurfaces,which consist of curly nano-cantilevers.The unidirectional reflectionless effect results from the asymmetric resonance at 1420 nm.The reflection is nearly 0 for the forward incidence,but is very high for the backward incidence.The reflectance difference reaches 56%.The preparation of the bending metamaterials not only implies that the potential applications of 3D architectures in photonic devices,but also provides an inspiration in the design of stereo devices.