Atomically Precise, Low-cost Manufacturing of Plasmonic Nano-Gaps for Chemical Sensing, Health Diagnostics and Optical Communication

等离子体纳米结构之所以引起人们的极大兴趣，是因为它们能够将光集中到一个小体积内，这可以导致许多潜在的应用。虽然理论上预测最佳的等离子体热点是两个金属颗粒之间小于1纳米的间隙，但目前还没有制造技术能够在实际成本下可靠地制造出高精度和可控的等离子体热点。该奖项将通过结合自上而下和自下而上的流程来解决这一关键障碍。模式是确定性定义的，自上而下，纳米间隙由原子层沉积的间隔层控制，自下而上，可以用原子精度控制。该技术可以在任意基片上以高通量和低成本绘制大面积的金属纳米缝隙。如果成功，这项技术不仅将为研究表面等离子激元极化和间隙等离子激元提供可靠的平台，而且还将使化学传感、疾病诊断和光通信方面的应用成为可能。此外，该项目还将成为激励初高中学生和代表性不足的少数民族学生学习和从事科学、技术、工程和数学（STEM）职业的示范展示。该项目的研究结果将被纳入纳米技术课程。虽然等离子体器件具有巨大的应用潜力，但目前还没有一种实用的制造技术能够满足这些器件的要求。关键的困难在于，这些器件中首选的低于1nm的金属间隙对于最先进的制造技术来说太小了。通过这个奖项，我们将通过使用可折叠的纳米手指模板转移打印金属纳米间隙结构来解决这一挑战。该模板由一个柔性纳米手指阵列和每个纳米手指顶部的金属帽组成。整个纳米指和纳米帽系统都用原子层沉积的方法覆盖了一层间隔层。将纳米手指样品浸入乙醇中风干后，毛细力使纳米手指顶部的盖子成对地坍塌在一起。然后通过转移印刷将这些塌陷的金属帽转移到目标基材上，并将间隔层蚀刻掉。以这种方式，转移印刷金属帽之间的间隙正好是间隔层的两倍厚。通过研究这一过程背后的基本原理，将开发出一种变革性的金属纳米间隙制造技术。

Plasmonic nanostructures are of great interest because of their ability to concentrate light to a small volume, which can lead to many potential applications. While it is theoretically predicted that the optimal plasmonic hot spot is a gap of less than 1 nanometer between two metallic particles, there is still no manufacturing technology to reliably fabricate it with high-precision and controllability at practical cost. This award will address this key roadblock by combining top-down and bottom-up processes. Patterns are deterministically defined, top-down, and the nano-gap controlled by a spacer layer deposited by atomic layer deposition, bottom-up, which can be controlled with atomic precision. This technology can pattern metallic nano-gaps over large area on arbitrary substrates at high throughput and low cost. If successful, not only will this technology provide a reliable platform to investigate surface plasmon polaritons and gap plasmons, but it will also enable applications in chemical sensing, disease diagnosis and optical communication. Moreover, this project will also be an exemplary showcase to motivate middle and high school students and under-represented minority students to study and pursue a career in science, technology, engineering and mathematics (STEM). The findings of this project will be integrated into a nanotechnology curriculum.While plasmonic devices have great application potential, there is no practical fabrication technology that meets the requirements of these devices. The key difficulty is that the sub-1nm metallic gap preferred in these devices is too small for state-of-the-art fabrication technologies. Through this award, we will tackle this challenge by transfer-printing metallic nano-gap structures using a collapsible nano-finger template. The template consists of a flexible nano-finger array and a metallic cap on top of each nano-finger. The entire system of nano-fingers and caps is coated with a spacer layer using atomic layer deposition. After the nano-finger sample is dipped into ethanol and air-dried, the capillary force makes the caps on top of nano-fingers collapse together in pairs. Then those collapsed metallic caps are transferred to the target substrate by transfer printing, and the spacer layer is etched away. In this way the gaps between the transfer-printed metallic caps are exactly twice as thick as the spacer layer. By studying the fundamentals behind this process, a transformative metallic nano-gap manufacturing technology will be developed.