Lithography-Free Manufacturing of Metal Structures Separated by Nanogaps

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This grant supports research that will advance the manufacturing techniques and knowledge base required for the on-chip fabrication of optical and electronic components composed of metal structures separated by nanometer-scale distances referred to as nanogaps. Despite proof-of-concept applications in chemical and biomedical sensing, nanoelectronics, and photovoltaics, progress in nanogap-based device processing is hampered by the need for technically demanding, time-consuming, and cost-prohibitive techniques. Moreover, current methods are far from ideal in terms of generating the configurations needed to fully express nanogap-related phenomena. This award aims to remedy this situation by transforming on-chip nanogap fabrication from processes that are inextricably complicated to those offering synthetic ease and unprecedented control while at the same time being responsive to the low-cost, high-throughput, and scalability needs of a manufacturing setting. The research carried out will be integrated into educational activities through graduate student training, undergraduate research internships, lab modules, and the mentorship of individuals participating in well-established programs promoting diversity, equity, and inclusion. The overall aim is, therefore, to advance applications of importance to the health and well-being of society while training the diverse workforce needed to enact leading-edge technologies. The objective of the award is to define the benchtop techniques required for the on-chip processing of opposing metal surfaces separated by sub-5 nm nanogaps as they relate to plasmonics and molecular electronics. Specifically targeted is the fabrication of (i) dimer arrays where the nanogap is occupied by molecular linkers, (ii) dimer arrays with air-filled nanogaps, and (iii) patterned electrodes connected by a bridge with a nanogap discontinuity along its length. Each of these forms a research thrust guided by an overall strategy in which nanoimprinting provides for deterministic positioning, a spacer material defines the nanogap width, and structures formed through liquid-state syntheses form a nanogap by butting up against a spacer material. The use of a spacer material is crucial to the overall approach in that nanogap definition is reliant, not on lithography, but on materials that are readily applied with monolayer-scale precision. Such capabilities, once demonstrated, will provide a path forward for integrating nanogaps into application platforms and provide new capabilities to the community of researchers prototyping state-of-the-art devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.