Excitonic electroabsorption effects in macroscopically aligned carbon nanotubes

Non-technical Description Carbon nanotubes have gained tremendous interest as a nanomaterial with potential to enable next generation optoelectronic devices. Individual nanotubes have a strong change in light absorption under an applied electric field, a phenomenon called electroabsorption. This makes them a promising candidate for high-speed electro-optic modulators, crucial components for applications such as optical communication, computing, and quantum information processing. Key to leveraging nanotube properties will be to align large numbers of them up to macroscopic scales. This project will use an intelligent autonomous self-assembly system to achieve macroscopically aligned semiconducting carbon nanotube films and then study their electro-optical properties. The research findings from this project could lead to a new material platform and lay the foundation for future technologies. The PI will also work to expand participation in STEM through training and education activities in the laboratory, classroom, and through outreach programs. The goal of these activities is to develop a diverse future STEM workforce. Technical Description Electroabsorption in conventional bulk semiconductors result in weak optical modulation, requiring large driving electric field and switching energy, and are sensitive to temperature variations. Semiconductor quantum wells can address first two challenges but still suffer from sensitive temperature dependency, require sophisticated manufacturing and engineering, and sometimes cryogenic device operations. Nanomaterials are emerging as new high-performance, versatile, and easy-to-manufacture room-temperature material platforms. However, current demonstrations of electroabsorption effects in macroscopic materials are limited. This project focuses on the direct experimental optical spectroscopy demonstration of the excitonic electroabsorption effects in macroscopic films of highly aligned and densely packed single-type semiconducting carbon nanotubes, which are manufactured through a self-assembly system and driven under static electric field. The goal of this project is to establish the manufacturing platform of such macroscopic carbon nanotube ensembles and explore the optical spectroscopy evidence of their electroabsorption effects. Specifically, the principal investigator develops a closed-loop, automatic, and machine-learning-assisted vacuum filtration system toward the fabrication of macroscopic films of aligned single-electronic-type carbon nanotubes. In addition, the principal investigator performs optical spectroscopy studies to explore electroabsorption effects in aligned films of a few representative semiconducting carbon nanotubes with different diameters. 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.