Atomic Layer Lithography for Integrated Optoelectronic Devices with Sub-10-nm Critical Dimensions

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Nontechnical description: In this project the PI will use an advanced nanofabrication technique called atomic layer lithography to create tiny gaps between metallic electrodes. The gaps can be as small as 1 nanometer across and centimeters long with nearly any geometry, including linear, curved or closed loops. Metallic nanogaps with these dimensions have unique electrical and optical properties. When an AC voltage is applied across the nanogaps, a phenomenon called dielectrophoresis is observed. Dielectrophoresis results in forces that can attract or repel small particles from the gaps. In this way the gaps can be used to trap or sort small biologically-relevant particles for further analysis with optical or electrical techniques. By shrinking the gap between electrodes to nanoscale dimensions, the dielectrophoretic forces can be orders of magnitude larger than with electrodes fabricated with traditional techniques. Additionally, these gaps can be integrated into nanoscale transistors that incorporated 2-dimensional materials like graphene. These nanogaps interact with electromagnetic radiation ranging from visible/infrared light to microwave radiation. The nanogaps strongly amplify optically-generated electromagnetic fields, which can be exploited for sensing interactions between molecules in solution and particles trapped along the gap. By creating nanogaps that can simultaneously trap biological particles and probe them with nanogap-enhanced optical techniques, this project will enable ultra-sensitive chemical analysis. This project also includes educational and outreach components, such as the training of high school, undergraduate and graduate students. The PI also maintains a relationship with the Science Museum of Minnesota and leads an annual activity station during the museum's NanoDays on the impacts of nanotechnology on everyday life. Technical description:The goal of this project is to design, fabricate, and characterize new devices with sub-10-nm electrically controllable metallic gaps that will enable a series of novel optical and electrical experiments. Atomic layer deposition will be utilized as a lithographic patterning method - atomic layer lithography - to produce electrically contacted metallic gaps with atomic-scale thickness resolution. Independent control of the gap thickness and contour shape allows for broadband and precise tuning of the electromagnetic resonance. The integration of electrical interconnects will enable new functionality of the nanogaps and a platform to demonstrate their potential applications. The nanogap devices will be integrated with 2D materials, turning the metal on either side of the gap into source and drain contacts of field-effect transistors and photodetectors. These example experiments will serve to entice experimental experts to utilize atomic layer lithography technique and also use nanogaps as a platform for their research. Intellectual Merit: To date, most researchers rely on electron-beam lithography to create nanogap structures. While suitable for proof-of-concept experiments, these techniques make integration into more complex devices difficult, since they are places where precisely defined geometries and patterns are needed. The intellectual merit of the proposed research is that the PI will transform atomic layer deposition as a top-down patterning method, thereby converting its precise thickness control into lateral patterning resolution without using electron-beam lithography. Electrical interconnects will be integrated to expand the capabilities of the devices. Example experiments in optoelectronics and nanoparticle trapping have the potential to make a large impact on the respective fields. Broader Impacts: If successful, the proposed atomic layer lithography technique will allow researchers the ability to create ultra-long single-digit nanogaps with built-in electrodes Therefore, this proposal has the potential to transform the fields of 2D materials optoelectronics. Graduate and undergraduate students will gain experience in nanofabrication and characterization. For K-12 outreach, the PI's team will build an interactive Activity Station at the Science Museum of Minnesota.