RUI: Atomically flat 3D metal-2D layered semiconductor devices for electronic and optoelectronic applications

RUI：用于电子和光电应用的原子扁平3D金属-2D层状半导体器件该奖项的全部或部分资金来自《2021年美国救援计划法案》(Public Law 117-2)。这项研究的重点是开发一种超灵敏的、千兆赫速度的紫外线(UV)光电探测器。快速响应和高灵敏度的紫外光探测器具有广泛的应用前景，从火灾监测、生物分析、环境传感器、空间探测到紫外线辐射检测，因此需求量很大。目前，还没有这样高效、快速的半导体纳米级光电探测器。开发这种器件的一个根本障碍是在半导体和金属电极之间建立理想的接触。几乎没有粗糙度的金属表面(原子平整表面)与2D半导体形成了理想的接触。这项研究将研究基于原子薄2D半导体-原子扁平金属接触的器件，以了解其基本的光电特性，并将其用于紫外区的应用，最终开发出一种新的超快、快速响应和高灵敏度的紫外光探测器。这项研究预计将产生重大的技术影响，范围从日常生活到新的通信工具。它将在一个以本科为主的机构进行，将涉及本科生和硕士学生，以及当地高中的学生。来自代表性不足群体的学生积极参与该项目，将为代表性不足群体提供尖端纳米科学研究经验，并提供一个培训纳米级光电子学的绝佳机会，为学生在工业和学术界的职业生涯做准备。原子薄的范德华晶体表现出显著的电学、光学和光电性能。该项目将研究单层过渡金属二卤化物(TMD)与原子平坦的Au表面电连接的器件，并研究其光电性质，以促进对开发纳米级固态紫外光探测器的基础认识。传统的金属蒸发和沉积形成金属-2D半导体结，不可避免地会导致半导体-金属结处的化学无序和费米能级钉扎。在这个项目中，将使用一种新开发的制造技术来制造理想的2D半导体和原子平坦的Au(AFAu)平面。三种不同类型的纳米器件将被广泛研究：(I)金属-绝缘体-金属肖特基二极管，(Ii)金属-绝缘体(六方氮化硼(HBN))-半导体-绝缘体-金属单量子阱器件，以及(Iii)由夹在两个原子平面之间的原子薄的单层TMD衍生的金属-半导体-金属光电探测器。该方案的目标是研究：(I)原子薄AFAu/hBN/AFAu肖特基异质结二极管的电子输运；(Ii)由AFAu/hBN/TMDS/hBN/AFAu制成的单量子阱的电子输运；(Iii)基于原子扁平金属电极的TMD半导体实现超灵敏光电子器件。这项研究将阐明理想的无无序、无费米能级钉扎的金属-半导体界面的电子输运。此外，这项关于理想金属-半导体界面的研究可能会给纳米电子学和纳米光子学领域带来革命性的变化，不仅是在2D系统中，而且在从能量收集到激子晶体管的其他纳米系统中也是如此。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

RUI: Atomically flat 3D metal-2D layered semiconductor devices for electronic and optoelectronic applicationsThis award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). This research focuses on developing an ultrasensitive, gigahertz speed photodetector in the ultraviolet (UV) range. Fast-response and high-sensitivity ultraviolet photodetectors are in high demand due to their potential for widespread applications ranging from fire monitoring, biological analysis, environmental sensors, and space exploration to UV radiation detection. Currently, such an efficient and fast semiconductor-based nanoscale photodetector is not available. One fundamental obstacle in developing such a device is to create an ideal contact between a semiconductor and a metallic electrode. Metal surface with almost no roughness (atomically flat surfaces) creates an ideal contact with a 2D semiconductor. This research will study devices based on atomically thin 2D semiconductors-atomically flat metal contacts to understand the basic optoelectronic properties and to utilize them for applications in the UV region and ultimately for the development of a new ultrafast, fast-response, and high-sensitivity UV photodetector. This research is expected to have significant technological impacts ranging from everyday life to new communication tools. It will be conducted at a Primarily Undergraduate Institution and will involve undergraduate and Master's students, and students from local high schools. The active participation of students from underrepresented groups in the project will provide a cutting-edge nanoscience research experience for underrepresented groups and an outstanding opportunity to train in nanoscale optoelectronics preparing students for careers in industry and academia. Atomically thin van der Waals crystals demonstrate remarkable electronic, optical, and optoelectrical properties. The project will study devices made of monolayer transition metal dichalcogenides (TMDs) electrically connected with atomically flat Au surface and investigate the optoelectronic properties to advance the fundamental understanding to develop a nanoscale solid-state UV photodetector. The conventional metal evaporation and deposition to create a metal-2D semiconductor junction causes inevitable chemical disorder and Fermi-level pinning at the semiconductor-metal junctions. In this project, a newly developed fabrication technique will be employed to make ideal 2D semiconductor and atomically flat Au (AFAu) planes. Three different types of nanoscale devices will be extensively studied; (i) metal-insulator-metal Schottky diodes, (ii) metal-insulator (hexagonal boron nitride(hBN))-semiconductor-insulator-metal single quantum well devices, and (iii) metal-semiconductor-metal photodetector derived from atomically thin monolayer TMDs sandwiched between two atomically flat metal planes. The objectives of the proposal are to study: (i) electronic transport of atomically thin AFAu/hBN/AFAu Schottky heterojunction diodes, (ii) electronic transport of single quantum well made of AFAu/hBN/TMDs/hBN/AFAu, (iii) realizing ultrasensitive optoelectronics devices based on TMD semiconductors with atomically flat metal electrodes. This research will elucidate the electronic transport across an ideal disorder-free and Fermi level pinning-free metal-semiconductor interface. Furthermore, this research on the ideal metal-semiconductor interface may revolutionize the field of nanoelectronics and nanophotonics, not only in 2D systems but also in other nanoscale systems ranging from energy harvesting to excitonic transistors.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.