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

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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.