Department of Electrical and Computer Engineering, ‡Center for Metamaterials and Integrated Plasmonics, §Department of Biomedical Engineering, and ∥Department of Chemistry, Duke University , Durham, North Carolina 27708, United States.
Nano Lett. 2013;13(12):5866-72. doi: 10.1021/nl402660s. Epub 2013 Nov 12.
A metallic nanoparticle positioned over a metal film offers great advantages as a highly controllable system relevant for probing field-enhancement and other plasmonic effects. Because the size and shape of the gap between the nanoparticle and film can be controlled to subnanometer precision using relatively simple, bottom-up fabrication approaches, the film-coupled nanoparticle geometry has recently been applied to enhancing optical fields, accessing the quantum regime of plasmonics, and the design of surfaces with controlled reflectance. In the present work, we examine the plasmon modes associated with a silver nanocube positioned above a silver or gold film, separated by an organic, dielectric spacer layer. The film-coupled nanocube is of particular interest due to the formation of waveguide cavity-like modes between the nanocube and film. These modes impart distinctive scattering characteristics to the system that can be used in the creation of controlled reflectance surfaces and other applications. We perform both experimental spectroscopy and numerical simulations of individual nanocubes positioned over a metal film, finding excellent agreement between experiment and simulation. The waveguide mode description serves as a starting point to explain the optical properties observed.
置于金属膜上的金属纳米粒子作为一个高度可控的系统具有很大的优势，可用于探测场增强和其他等离激元效应。由于使用相对简单的自下而上的制造方法可以将纳米粒子和膜之间的间隙的大小和形状控制到亚纳米精度，因此最近已经将膜耦合纳米粒子几何形状应用于增强光学场、进入等离激元的量子领域以及设计具有受控反射率的表面。在本工作中，我们研究了置于银或金膜上的银纳米立方体所关联的等离激元模式，其间由有机介电间隔层隔开。由于纳米立方体和膜之间形成了类似于波导腔的模式，因此膜耦合纳米立方体特别有趣。这些模式赋予了系统独特的散射特性，可用于创建受控反射率表面和其他应用。我们对置于金属膜上的单个纳米立方体进行了实验光谱和数值模拟，发现实验和模拟之间具有极好的一致性。波导模式描述可作为解释观察到的光学性质的起点。
