State Key Lab of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, P.R. China.
Nanoscale. 2019 Feb 21;11(8):3583-3590. doi: 10.1039/c8nr08946a.
We combine anisotropic wet etching and nanoskiving to create a novel three-dimensional (3D) nanoantenna for plasmonic nanofocusing, vertically aligned zig-zag nanogaps, constituted of nanogaps with defined angles. Instead of conventional lithography, we used the thickness of a self-assembled monolayer (SAM) to define nanogaps with high throughput, and anisotropic etching of Si V-grooves to naturally define ultra-sharp tips. Both nanogaps and sharp tips can synergistically squeeze the electro-magnetic (EM) field and excite 3D nanofocusing, enabling great potential applications in chemical sensing and plasmonic devices. The dependence of the EM field enhancement on structural features is systematically investigated and optimized. We found that the field enhancement and confinement are stronger at the tipped-nanogap compared to what standalone tips or nanogaps produce. The intensity of surface-enhanced Raman spectroscopy (SERS) recorded on the 70.5° tipped-nanogaps is 45 times higher than that recorded with linear nanogaps and 5 times higher than that recorded with tip-only nanowires, which is attributed to the integration of the tip and gap in plasmonic nanostructures. This proposed nanofabrication technique and the resulting structures equipped with a strongly enhanced EM field will promote broad applications for nanophotonics and surface-enhanced spectroscopy.
我们结合各向异性湿法刻蚀和纳米切割技术，创建了一种新颖的三维（3D）纳米天线，用于等离子体纳米聚焦，垂直排列的锯齿形纳米间隙由具有确定角度的纳米间隙组成。我们没有使用传统的光刻技术，而是利用自组装单分子层（SAM）的厚度进行高通量纳米间隙定义，并通过各向异性的硅 V 型槽刻蚀来自然定义超锐利的尖端。纳米间隙和尖锐的尖端可以协同挤压电磁场并激发 3D 纳米聚焦，在化学传感和等离子体器件等领域有很大的应用潜力。我们系统地研究和优化了电磁场增强对结构特征的依赖性。我们发现，与独立的尖端或纳米间隙相比，在带尖端的纳米间隙处的电磁场增强和限制更强。在 70.5°带尖端的纳米间隙上记录的表面增强拉曼光谱（SERS）强度比线性纳米间隙记录的强度高 45 倍，比仅带尖端的纳米线记录的强度高 5 倍，这归因于在等离子体纳米结构中整合了尖端和间隙。这种提出的纳米制造技术和由此产生的具有强电磁场增强的结构将促进纳米光子学和表面增强光谱学的广泛应用。
