Microellipsometric investigation of ordered plasmonic nanostructures

本项目致力于利用角分辨消光光谱和高空间分辨率成像光谱椭圆偏振光谱仪研究有序等离子体纳米结构。用于这些研究的结构是通过电子束光刻制备的。柱状纳米颗粒排列成有序的格子，放置在隔离物上，将这些颗粒与额外的金属层(所谓的金属-绝缘体-金属(MIM)结构)隔开。这种体系具有多种电磁共振，除了所用材料外，其光谱和几何位置还可以通过组成纳米粒子的几何参数、晶格参数和间隔物的厚度来调节。与纳米颗粒的随机分布相比，晶格形状因子应该提供一个额外的通道来管理具有相同填充比例的纳米颗粒但不同类型的晶格的这类系统的响应。在不同入射角下使用消光和成像椭偏测量将允许激发和分离系统的纵向和横向共振，揭示单独的、晶格的和合作的共振，并不仅提供幅度信息，而且还提供相位信息。后者将有助于揭示这类系统中的不同相互作用。拉曼光谱将被用来揭示所研究结构的局域等离子体近场增强，而随后的间隔体的刻蚀将有助于评估带隙模式的作用。将使用的椭偏仪系统的附加选项使其能够与原子力显微镜(AFM)相结合，以确定纳米颗粒在晶格中的真实排列及其取向。这些附加信息在分析这些结构的等离子体性质时可能非常有价值。

This project is devoted to the investigation of ordered plasmonic nanostructures by angle-resolved extinction spectroscopy and imaging spectro-ellipsometry with high spatial resolution. Structures for these investigations are prepared by electron beam lithography. Cylindrical nanoparticles are arranged in ordered lattices on a spacer separating those particles from an additional metallic layer (so-called metal-insulator-metal (MIM) structures). Such a system has a variety of electromagnetic resonances, spectral and geometrical position of which may be tuned besides the used materials by the geometrical parameters of the constituting nanoparticles, the lattice parameters, and the thickness of the spacer. In contrast to random distributions of nanoparticles, the lattice form-factor should provide an additional channel to manage the response of such systems with the same filling fraction of nanoparticles but different kinds of lattices. The use of extinction and imaging ellipsometry at different angles of incidence will allow both longitudinal and transverse resonances of the system to be excited and separated, revealing individual, lattice, and cooperative resonances as well as providing not only amplitude but phase information. The latter will help to reveal different interactions in such systems. Raman spectra will be taken to reveal the local plasmonic near-field enhancement of the investigated structures, while subsequent etching of the spacer will help to evaluate the role of the gap modes. The additional options of the ellipsometer system to be used enable the combination with atomic force microscopy (AFM) to determine the real arrangement of nanoparticles in the lattice and its orientation. Such additional information can be very valuable in the analysis of plasmonic properties of these structures.