Resonant Gap Nanoparticle Chains, with Application to Surface Enhanced Raman Scattering

目的：设计和比较基于共振间隙模式的金属二聚体、缝隙腔体和纳米粒子链光学结构，以便得到可用于制造的候选设计。采用高分辨率光刻、原子层沉积和选择性刻蚀的方法制作线宽为2~10 nm的介质栅。这种光栅将被压印在金属薄膜上，形成光滑而狭窄的沟槽，从而实现设计的谐振槽和链波导。为了评估场增强和导引性能，将使用近场和远场方法作为波长的函数来测试装配式结构。拉曼测量将被用来确定增强。智能优点：具有共振间隙的纳米粒子可以为非线性光学和光谱学提供大场增强。将要开发的制造技术将达到几纳米的线宽，这是一个非常有兴趣的长度尺度，但标准的自上而下光刻无法达到。广泛的影响：两名博士生将得到支持，这项研究将构成他们论文的重要部分。每年将邀请一名本科生参与这个项目。这项研究的材料将在韦伯和齐教授的初级研究生和高级本科课程中用作演示，并适当地纳入普渡大学EPICS(社区服务工程项目)，这是为本科生提供的设计体验。开发的模拟工具将可通过普渡调查人员的网站获取。

Objective:Metal dimer, slot-cavity, and nanoparticle chain optical structures that operate based on resonant gap modes will be designed and compared using numerical electromagnetic simulations, in order to arrive at candidate designs for fabrication. Dielectric gratings with 2-10 nm line width will be fabricated with high-resolution lithography, atomic layer deposition and selective etching. Such gratings will be imprinted into metal films to form smooth and narrow trenches, thereby achieving designed resonant slot and chain waveguides. Fabricated structures will be tested using near-field and far-field approaches as a function of wavelength, in order to evaluate field enhancement and guiding performance. Raman measurements will be performed to determine the enhancement.Intellectual Merit:Nanoparticles with resonant gaps can provide large field enhancement for nonlinear optics and spectroscopy. The fabrication techniques to be developed will achieve line widths of a few nanometers, a length scale of tremendous interest yet not accessible with standard top-down lithography.Broader Impacts:Two Ph.D. students will be supported, and this research will constitute a substantial part of their theses. An undergraduate research student will be invited to work on this project each year. Material from this research will be used as demonstrations in entry-level graduate and senior-level undergraduate classes taught by Webb and Qi, and incorporated, as appropriate, into Purdue EPICS (engineering projects in community service), a design experience for undergraduates. Simulation tools developed will be accessible through the investigators Purdue web sites.