Schubert Ina, Sigle Wilfried, van Aken Peter A, Trautmann Christina, Toimil-Molares Maria Eugenia
GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstr. 1, Darmstadt, Germany.
Nanoscale. 2015 Mar 21;7(11):4935-41. doi: 10.1039/c4nr06578f.
Surface plasmon coupling in nanowires separated by small gaps generates high field enhancements at the position of the gap and is thus of great interest for sensing applications. It is known that the nanowire dimensions and in particular the symmetry of the structures has strong influence on the plasmonic properties of the dimer structure. Here, we report on multipole surface plasmon coupling in symmetry-broken AuAg nanowire dimers. Our dimers, consisting of two nanowires with different lengths and separated by gaps of only 10 to 30 nm, were synthesized by pulsed electrochemical deposition in ion track-etched polymer templates. Electron energy-loss spectroscopy in scanning transmission electron microscopy allows us to resolve up to nine multipole order surface plasmon modes of these dimers spectrally separated from each other. The spectra evidence plasmon coupling between resonances of different multipole order, resulting in the generation of additional plasmonic modes. Since such complex structures require elaborated synthesis techniques, dimer structures with complex composition, morphology and shape are created. We demonstrate that finite element simulations on pure Au dimers can predict the generated resonances in the fabricated structures. The excellent agreement of our experiment on AuAg dimers with finite integration simulations using CST microwave studio manifests great potential to design complex structures for sensing applications.
由小间隙分隔的纳米线中的表面等离子体激元耦合在间隙位置产生高场增强，因此在传感应用中备受关注。众所周知，纳米线尺寸，特别是结构的对称性对二聚体结构的等离子体特性有很大影响。在此，我们报道了对称性破缺的金银纳米线二聚体中的多极表面等离子体激元耦合。我们的二聚体由两根不同长度的纳米线组成，间隙仅为10至30纳米，通过脉冲电化学沉积在离子径迹蚀刻的聚合物模板中合成。扫描透射电子显微镜中的电子能量损失谱使我们能够在光谱上分辨出这些二聚体的多达九个多极阶表面等离子体激元模式，它们彼此分离。光谱证明了不同多极阶共振之间的等离子体激元耦合，导致产生额外的等离子体激元模式。由于这种复杂结构需要精细的合成技术，因此创建了具有复杂组成、形态和形状的二聚体结构。我们证明，对纯金二聚体的有限元模拟可以预测所制造结构中产生的共振。我们对金银二聚体的实验与使用CST微波工作室进行的有限积分模拟的出色一致性表明，设计用于传感应用的复杂结构具有巨大潜力。
