Closing the terahertz gap with a new-family of terahertz devices based on two-dimensional materials

（非技术）该项目的目标是开发新一代电子设备，能够在远高于当前最先进的电子设备所能达到的频率下有效地工作，进入太赫兹频谱区域。 在过去的十年中，太赫兹频率范围，位于微波和红外之间的电磁频谱区域，由于其在天文学、成像、光谱学、安全、通信等不同领域的广泛独特应用而成为备受关注的主题。虽然最近取得了重大进展，仍然需要在这些频率下有效工作的设备。 特别地，需要低成本、紧凑的太赫兹辐射源。 在这种情况下，该提案中针对的研究试图为太赫兹社区长期存在的问题提供答案：如何在室温下在紧凑的电子设备中实现太赫兹频率下的功率增益。 所提出的器件可以提供低制造成本，因此将在未来的紧凑型太赫兹系统中找到许多潜在的工业应用（例如，用于通信、安全和生物医学应用的“太赫兹芯片”）。 这一研究愿景与指导材料，高频电子，太赫兹和光学领域的新一代研究生和本科生的教育愿景交织在一起，并通过为他们提供实践经验来激发他们的批判性思维和好奇心。 考虑到美国，特别是犹他州未来对训练有素的工程师和科学家的需求，这一点非常重要。 拟议的研究和教育计划将利用正在进行的材料，电子和光电子学研究活动以及犹他州大学目前的推广计划。（技术）本项目的目的是开发基于二维材料层的共振隧穿和电子等离子体波之间相互作用的有源太赫兹电子器件（太赫兹探测器、振荡器和放大器）。 这些器件在放大器配置中，在2 THz以上的频率下保证7 dB的功率增益，这在传统的高频电子器件中已经被证明是难以实现的。 在这些器件中实现太赫兹频率增益的基本机制是负微分电导（NDC）与二维电子气（2DEG）中的电子等离子体波之间的相互作用，即NDC为半导体2DEG中激发的等离子体波提供增益介质。 与这些器械相关的所有挑战都将在材料、器械制造和设计阶段得到识别和解决。 在这些2D材料中，石墨烯由于其大的室温迁移率因此低的等离子体阻尼而可以是用于等离子体传输的优良平台。 此外，其固有的2D性质及其易于转移到任意衬底可以允许无限的集成自由度，相对于III-V族半导体降低成本，并允许更简单的制造工艺。我们还将回答有关高质量2D材料制备的问题：域尺寸的控制和优化，完整性，夹杂物，界面边界，污染，堆叠层之间的晶体学/对齐保真度，以及终止碳键合。

(Non-Technical) The goal of this project is to develop a new generation of electronic devices capable of efficiently operating at frequencies well above those attainable in current state-of-the-art electronic devices, into the terahertz region of the spectrum. Over the past decade, the terahertz frequency regime, the region of the electromagnetic spectrum located between the microwave and the infra-red, has become the subject of much attention due to its wide range of unique applications in diverse areas such as astronomy, imaging, spectroscopy, security, communications, and so on. Although significant progress has been recently achieved, there is still a need for devices efficiently operating at these frequencies. In particular, there is a necessity for low-cost, compact sources of terahertz radiation. In this context, the research targeted in this proposal tries to provide an answer for a long standing problem for the terahertz community: how to achieve power gain at terahertz frequencies in compact, electronic devices at room-temperature. The proposed devices can offer low cost of manufacturing, and therefore will find many potential industrial applications in future compact terahertz systems (e.g. "terahertz chips" for communications, security, and biomedical applications). This research vision is interlaced with an educational vision of mentoring new generations of graduate and undergraduate students in the field of materials, high frequency electronics, terahertz, and optics and stimulating their critical thinking and curiosity by providing them with hands-on experience in cutting-edge research. This is of significant importance given the future projected needs for highly trained engineers and scientists in the United States, and in particular in the state of Utah. The proposed research and educational plans will leverage the ongoing research activities on materials, electronics and optoelectronics and the current outreach programs at the University of Utah.(Technical) This project aims to develop active terahertz electronic devices (terahertz detectors, oscillators, and amplifiers) based on the interplay between resonant tunneling and electron plasma waves in stacked two-dimensional material layers. These devices promise power gains 7dB at frequencies above 2 THz when in amplifier configurations, which has been proven to be difficult to achieve in traditional high-frequency electronic-devices. The fundamental mechanism enabling gain at terahertz frequencies in these devices is the interplay between negative differential conductance (NDC) and the electron plasma waves in a two-dimensional electron gas (2DEG), i.e. the NDC provides a gain medium for the plasma waves excited in the semiconductor 2DEG. All the challenges associated with these devices are going to be identified and addressed at the materials, device fabrication, and design stages. Of these 2D materials, graphene, can be an excellent platform for plasmonic transport owed to its large room temperature mobility thus low plasmonic damping. Moreover, its intrinsic 2D nature, and its ease of transfer to arbitrary substrates can allow for unlimited degrees of freedom of integration, reduce the cost with respect to that in III-V semiconductors, and allow for more simple fabrication processes. We will also answer questions regarding high quality 2D material preparation: control and optimization of domain size, integrity, inclusions, interface boundaries, contamination, fidelity of crystallography / alignment between stacked layers, and terminating carbon bonding.