Arrays of Plasmonic Nanoparticle Dimers with Defined Nanogap Spacers.

Eunjin Choi,Mariana Alarcón-Correa,Peer Fischer,Cornelia Miksch,Hyeon-Ho Jeong,Alison F. Mark,Jan-Philipp Günther,Melanie C. Adams,Andrew G. Mark,Insook Kim

doi:10.1021/acsnano.9b04938

Eunjin Choi, Mariana Alarcón-Correa

Open Access

https://doi.org/10.1021/acsnano.9b04938

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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 meta-molecules 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.

Highlights

Plasmonic building blocks that mimic molecular structures with a nanometer gap show strong optical near-field coupling.[1]
Control of a second angle, the azimuthal axis of rotation φ, leads to the change in the vapor flux direction relative to the substrate allowing the growth of more complex structures (Figure 1h). Controlling these two angles independently allows one to grow 3D-shaped nanostructures.[20,24−26] The material composition and sequence of materials within a structure can be freely chosen during the growth.[27−32] Here we describe how to extend this capability to obtain plasmonic dimer and trimer structures separated by precise nanogaps
Breaking the symmetry of the plasmonic dimers permits plasmonic band engineering, but it is generally difficult to realize.[10,44−47] We show that the barrier-aided asymmetric shadow growth can be used to fabricate an array of asymmetric in-plane dimers on a ∼ 2 in. glass substrate, Figure 5a

Summary

Introduction

Plasmonic building blocks that mimic molecular structures with a nanometer gap show strong optical near-field coupling.[1]. Control of a second angle, the azimuthal axis of rotation φ, leads to the change in the vapor flux direction relative to the substrate allowing the growth of more complex structures (Figure 1h) Controlling these two angles independently allows one to grow 3D-shaped nanostructures.[20,24−26] The material composition and sequence of materials within a structure can be freely chosen during the growth.[27−32] Here we describe how to extend this capability to obtain plasmonic dimer and trimer structures separated by precise nanogaps

Methods

Findings

Conclusion