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

目的：设计并比较基于谐振间隙模式的金属二聚体、槽腔和纳米颗粒链光学结构，并利用数值电磁模拟得出候选的制造设计。采用高分辨率光刻、原子层沉积和选择性蚀刻技术制备线宽为2 ~ 10nm的介质光栅。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。制造的结构将使用近场和远场方法作为波长的函数进行测试，以评估场增强和引导性能。将进行拉曼测量来确定增强。知识优势：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。有待开发的制造技术将实现几纳米的线宽，这是一个非常有趣的长度尺度，但标准的自顶向下光刻技术无法实现。更广泛的影响：将支持两名博士生，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研究生参与该项目。本研究的材料将在Webb和Qi教授的入门级研究生和高级本科课程中用作演示，并酌情纳入普渡大学EPICS（社区服务工程项目），这是本科生的设计体验。开发的模拟工具将可通过研究人员的普渡大学网站访问。

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.