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

非技术总结在提高计算速度的需要的推动下，研究人员不断地寻找超越当今微电子工业极限的方法。一种替代方案是使用光而不是电子。因此，科学家和工程师一直在开发基于金属而不是半导体的设备，这种设备可以将光压缩到极其微小的结构中(不到人类头发厚度的千分之一，即纳米级)。这些所谓的等离子体器件的性能在很大程度上取决于金属的光学响应，例如，有多少光被传输、反射和吸收。到目前为止，金属积木是由硬币时代的金属，如金、银和铜制成的，具有明确的颜色，因此具有预定的光学特性。为了克服用于纳米级等离子激元的纯金属的现有局限性，马里兰大学的莱特小组将研究混合金属或合金的光学响应。为此，他们将通过混合Au、Ag、Cu和Al来设计和制造合金化薄膜和纳米结构，并使用一系列表征工具来模拟/测量它们在光照下的行为。控制合金金属的光学性质可以极大地促进纳米级光子学、光伏和传感器领域的发展。该项目将涉及STEM中代表性不足群体的高中生和本科生，通过为他们提供在材料科学方面进行研究的机会，帮助他们获得领先的科学和技术职业。该项目的科学发现将通过视觉上吸引人的插图广泛传播，向公众推广科学和工程学。技术综述纳米光子器件的未来发展关键取决于构成结构的金属构件的介电功能。该方案的研究目标是开发和实现一类新的具有可调光学性质的金属薄膜和纳米结构，即介电功能。为此，莱特团队将把计算材料科学与实验研究相结合，设计和制造由银、金、铜和铝形成的合金薄膜和纳米结构。这些合金的光学响应将用椭偏仪和近场光学显微镜来表征。合金纳米颗粒将应用于太阳能电池，通过增加半导体内部的光吸收来改善器件性能。这项研究将通过将冶金和等离子两个几乎正交的领域结合起来，推动基础材料科学的发展，使设计和制造具有自然界中没有的按需光学响应的金属合金纳米结构成为可能。这些光学材料的发展可能会对未来的纳米光子设备产生潜在的变革性影响，因为它能够完全控制它们的介电功能，从而创造出优异的光学性能。虽然多个实验已经证明了如何使用纯金属来捕获太阳能电池中的光，但使用合金的实验和数值演示都没有。

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.