Rothe Martin, Zhao Yuhang, Kewes Günter, Kochovski Zdravko, Sigle Wilfried, van Aken Peter A, Koch Christoph, Ballauff Matthias, Lu Yan, Benson Oliver
Humboldt Universität zu Berlin & IRIS Adlershof, Nanooptics, Newtonstraße 15, 12489, Berlin, Germany.
Helmholtz Zentrum Berlin für Materialien und Energie, Institute of Soft Matter and Functional Materials, Hahn-Meitner-Platz 1, 14109, Berlin, Germany.
Sci Rep. 2019 Mar 7;9(1):3859. doi: 10.1038/s41598-019-40380-5.
Metal nanoparticles are the most frequently used nanostructures in plasmonics. However, besides nanoparticles, metal nanowires feature several advantages for applications. Their elongation offers a larger interaction volume, their resonances can reach higher quality factors, and their mode structure provides better coupling into integrated hybrid dielectric-plasmonic circuits. It is crucial though, to control the distance of the wire to a supporting substrate, to another metal layer or to active materials with sub-nanometer precision. A dielectric coating can be utilized for distance control, but it must not degrade the plasmonic properties. In this paper, we introduce a controlled synthesis and coating approach for silver nanowires to fulfill these demands. We synthesize and characterize silver nanowires of around 70 nm in diameter. These nanowires are coated with nm-sized silica shells using a modified Stöber method to achieve a homogeneous and smooth surface quality. We use transmission electron microscopy, dark-field microscopy and electron-energy loss spectroscopy to study morphology and plasmonic resonances of individual nanowires and quantify the influence of the silica coating. Thorough numerical simulations support the experimental findings showing that the coating does not deteriorate the plasmonic properties and thus introduce silver nanowires as usable building blocks for integrated hybrid plasmonic systems.
金属纳米颗粒是等离子体激元学中最常用的纳米结构。然而，除了纳米颗粒外，金属纳米线在应用方面具有几个优势。它们的伸长提供了更大的相互作用体积，其共振可以达到更高的品质因数，并且其模式结构能够更好地耦合到集成的混合介质 - 等离子体激元电路中。不过，至关重要的是要以亚纳米精度控制金属线与支撑衬底、另一金属层或活性材料之间的距离。可以利用介电涂层来控制距离，但它不能降低等离子体激元特性。在本文中，我们介绍了一种用于银纳米线的可控合成和涂层方法，以满足这些要求。我们合成并表征了直径约为70纳米的银纳米线。使用改进的施托伯方法用纳米尺寸的二氧化硅壳包覆这些纳米线，以获得均匀且光滑的表面质量。我们使用透射电子显微镜、暗场显微镜和电子能量损失光谱来研究单个纳米线的形态和等离子体激元共振，并量化二氧化硅涂层的影响。全面的数值模拟支持了实验结果，表明该涂层不会降低等离子体激元特性，从而将银纳米线引入作为集成混合等离子体激元系统可用的构建块。
