Xiang Quan, Li Zhiqin, Zheng Mengjie, Liu Qing, Chen Yiqin, Yang Lan, Jiang Tian, Duan Huigao
School of Physics and Electronics, State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, People's Republic of China.
Nanotechnology. 2018 Mar 9;29(10):105301. doi: 10.1088/1361-6528/aaa691.
Elevated metallic nanostructures with nanogaps (<10 nm) possess advantages for surface enhanced Raman scattering (SERS) via the synergic effects of nanogaps and efficient decoupling from the substrate through an elevated three-dimensional (3D) design. In this work, we demonstrate a pattern-transfer-free process to reliably define elevated nanometer-separated mushroom-shaped dimers directly from 3D resist patterns based on the gap-narrowing effect during the metallic film deposition. By controlling the initial size of nanogaps in resist structures and the following deposited film thickness, metallic nanogaps could be tuned at the sub-10 nm scale with single-digit nanometer precision. Both experimental and simulated results revealed that gold dimer on mushroom-shaped pillars have the capability to achieve higher SERS enhancement factor comparing to those plasmonic dimers on cylindrical pillars or on a common SiO/Si substrate, implying that the nanometer-gapped elevated dimer is an ideal platform to achieve the highest possible field enhancement for various plasmonic applications.
具有纳米间隙（<10纳米）的升高的金属纳米结构通过纳米间隙的协同效应以及通过升高的三维（3D）设计与基底的有效解耦，在表面增强拉曼散射（SERS）方面具有优势。在这项工作中，我们展示了一种无需图案转移的工艺，基于金属膜沉积过程中的间隙变窄效应，直接从3D抗蚀剂图案可靠地定义升高的纳米间隔蘑菇形二聚体。通过控制抗蚀剂结构中纳米间隙的初始尺寸和随后沉积的膜厚度，金属纳米间隙可以在亚10纳米尺度上以个位数纳米精度进行调节。实验和模拟结果均表明，与圆柱形柱体或普通SiO/Si基底上的等离子体二聚体相比，蘑菇形柱体上的金二聚体能够实现更高的SERS增强因子，这意味着纳米间隙升高的二聚体是实现各种等离子体应用中尽可能高的场增强的理想平台。
