Integrated Research and Education on Metal Alloys with On-Demand Optical Response

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NON-TECHNICAL SUMMARYMotivated by the need for improved computational speed, researchers are constantly searching for ways of surpassing the limit of today's microelectronics industry. One alternative is to use light instead of electrons. Thus, scientists and engineers have been developing devices based on metals instead of semiconductors, which can squeeze light into extremely small structures (less than one thousandth the thickness of a human hair, i.e. at the nanoscale). The performance of these so-called plasmonic devices heavily depends on the optical response of the metals, e.g., how much light is transmitted, reflected and absorbed. To date, the metallic building blocks are made of coin age metals, such as Au, Ag and Cu, with well defined color and, thus, pre-determined optical properties. In order to overcome the existing limitations of pure metals used in nanoscale plasmonics, the Leite group at the University of Maryland will investigate the optical response of mixed metals, or alloys. For that, they will design and fabricate alloyed thin films and nanoscale structures by mixing Au, Ag, Cu and Al, and model/measure their behavior upon illumination by using a set of characterization tools. Controlling the optical properties of alloyed metals can tremendously benefit the fields of nanoscale photonics, photovoltaics, and sensors. This project will involve high school and undergraduate students from under-represented groups in STEM to help them secure leading careers in science and technology by providing them with the opportunity to perform research in materials science. The scientific findings from this project will be widely disseminated through visually appealing illustrations, to promote science and engineering to the general public. TECHNICAL SUMMARYThe future development of nanophotonic devices critically depends on the dielectric function of the metallic building blocks composing the structures. The research objective of this proposal is to develop and implement a new class of metallic thin films and nanostructures with tunable optical properties, i.e., dielectric functions. For that, the Leite group will combine computational materials science with experimental research to design and fabricate alloyed thin films and nanostructures formed by Ag, Au, Cu and Al. The optical response of these alloys will be characterized by ellipsometry and near-field optical microscopy. Alloyed nanoparticles will be applied to solar cells to improve the device performance by increasing light absorption within the semiconductor. This research will advance fundamental materials science by combining two almost orthogonal fields, metallurgy and plasmonics, enabling the design and fabrication of metal-alloyed nanostructures with on-demand optical response not found in nature. The development of these optical materials may have a potentially transformative effect on future nanophotonic devices by enabling the complete control of their dielectric function and, therefore, creating superior optical performance. While multiple experiments have demonstrated how pure metals can be used to trap light inside solar cells, there are neither numerical nor experimental demonstrations using alloys.