Arrays of Plasmonic Nanoparticle Dimers with Defined Nanogap Spacers

Abstract

Plasmonic molecules are building blocks of metallic nanostructures that give rise to intriguing optical phenomena with similarities to those seen in molecular systems. The ability to design plasmonic hybrid structures and molecules with nanometric resolution would enable applications in optical metamaterials and sensing that presently cannot be demonstrated, because of a lack of suitable fabrication methods allowing the structural control of the plasmonic atoms on a large scale. Here we demonstrate a wafer-scale "lithography-free" parallel fabrication scheme to realize nanogap plasmonic metamolecules with precise control over their size, shape, material, and orientation. We demonstrate how we can tune the corresponding coupled resonances through the entire visible spectrum. Our fabrication method, based on glancing angle physical vapor deposition with gradient shadowing, permits critical parameters to be varied across the wafer and thus is ideally suited to screen potential structures. We obtain billions of aligned dimer structures with controlled variation of the spectral properties across the wafer. We spectroscopically map the plasmonic resonances of gold dimer structures and show that they not only are in good agreement with numerically modeled spectra, but also remain functional, at least for a year, in ambient conditions.

Laser‐Scanning‐Guided Assembly of Quasi‐3D Patterned Arrays of Plasmonic Dimers for Information Encryption

“…[ 9,10 ] Among others, dimeric clusters of plasmonic NPs show strong optical near‐field coupling and form hotspots in which the electromagnetic field is concentrated, depending on the interparticle distance, the orientation of NPs, and the size, shape and composition of NPs. [ 11–13 ] These unique properties have enabled enormous applications of plasmonic NP dimers in surface enhanced Raman spectroscopy (SERS) detection, [ 14,15 ] mask‐free ultrahigh resolution lithography, [ 16 ] enhanced chemical synthesis, [ 17 ] and nanopixel displays, [ 18 ] to name just a few. Existing strategies for assembling plasmonic NPs into dimers include electrostatic interaction‐regulated assembly, [ 19 ] assembly of site‐specifically functionalized NPs, [ 20,21 ] DNA origami‐templated assembly, [ 22,23 ] and stoichiometric reaction controlled NP bonding.…”

“…[ 35 ] However, as of now, the preparation of plasmonic dimer arrays with subwavelength resolution and arbitrary patterns remains a challenge. On one hand, the fabrication of plasmonic NP arrays heavily relies on the top‐down techniques, such as electron beam lithography, [ 36 ] dip‐pen lithography, [ 37 ] glancing angle physical vapor deposition, [ 12,38,39 ] and focused ion beam. These approaches show high precision in fabrication, but have limitations, including requirement of special equipment, difficulty of producing 3D structures, and presence of defects and grain boundaries in the resulting nanostructures.…”

Silver‐Coated Disordered Silicon Nanowires Provide Highly Sensitive Label‐Free Glycated Albumin Detection through Molecular Trapping and Plasmonic Hotspot Formation

“…In contrast, nanostructured substrates promise more reproducible enhancement, and a wide variety of plasmonic arrays have been proposed seeking to maximize the field enhancement at well‐defined locations and at targeted frequencies. [ 38–41 ]…”

“…In contrast, nanostructured substrates promise more reproducible enhancement, and a wide variety of plasmonic arrays have been proposed seeking to maximize the field enhancement at welldefined locations and at targeted frequencies. [38][39][40][41] Among such SERS-active substrates, silicon nanowires (SiNWs) coated by metal nanoparticles (NP) or thin films have recently emerged as promising tools for the detection of biomolecules. [42][43][44][45][46][47][48][49] These structures permit strong plasmonic enhancement while also offering an opportunity to combine huge surface-to-volume ratios, facile surface modification and full compatibility to well-established silicon technology.…”

Investigating photoresponsivity of graphene-silver hybrid nanomaterials in the ultraviolet

“…They also offer tunability in terms of spectral response, e.g., by changing the shape, size, and material, or polarizationresponse, e.g., by changing the aspect ratio. 11 By engineering the coupling between the plasmonic nanoparticles, 12,31 e.g., sandwiching the graphene between two plasmonic nanospheres, 13 extremely sensitive photodetectors have been developed, most of which operate in the visible to near IR wavelengths. So far, gold has been used most extensively in the literature due to its stable and nonoxidizing nature.…”