Development of tunnel field effect optoelectronic devices based on stacked 2D crystals with clean interfaces

非技术性：光通信的基础是通过激光器和光电二极管等光电器件将电信号转换为光信号。基于传统半导体（如硅）的器件正在达到性能的极限。石墨烯（一种二维（2D）碳层）的发现表明，当大块材料减薄到单层时，新的电子特性将如何出现。其他2D材料包括氮化硼、黑磷和过渡金属二硫属化物。不同的2D材料可以一次一层地组装成垂直堆叠的薄膜。这种异质结构可以实现单一材料不可能实现的功能和性能。不同2D材料之间的界面对于保持独特的特性至关重要，这些特性使它们对器件应用具有吸引力。主要研究者将使用新开发的清洁转移方法制备具有清洁界面的2D异质结构材料。一个定制的扫描探针显微镜与纳米级光源的尖端将被用来研究器件的光学和电子性能与前所未有的分辨率。 本计画的成果将丰富对这些材料的了解，并加速奈米光电子学的发展。这个跨学科的项目将研究整合到材料科学，工程和纳米制造的研究生和本科生的教育中。技术方面：本项目将结合联合收割机、新型二维异质结构材料制备技术、近场扫描光学显微镜和近场扫描光电流显微镜，研究基于货车瓦材料的异质结构的基本光电特性和光生载流子行为。光电流成像具有10nm以下的高空间分辨率，可以揭示纳米尺度上丰富的物理现象。这些包括局部pn结，域边界，边缘，掺杂剂和应变。对这些特征进行成像可以显着提高对这种新材料系统的电子和光子特性的理解和控制。该项目的目标是：（1）展示用于研究异质结构器件的原型双折射模式近场扫描光电流显微镜，（2）将扫描光电流成像技术的空间分辨率提高到亚10 nm水平，以及（3）研究基于石墨烯、氮化硼、透射金属二硫属化物（诸如WSe 2、MoS2和MoSe 2）的垂直堆叠异质结构的光响应性，以及（4）发展对纳米尺度特征的作用的基本理解，如边缘终止和层间缺陷形成对光电性能的影响。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical:Optical communication is based on converting electrical signals into optical signals by optoelectronic devices such as lasers and photodiodes. Devices based on conventional semiconductors such as silicon are reaching the ultimate limits for performance. New materials and structures are required to advance the state of the art. The discovery of graphene, a two-dimensional (2D) layer of carbon, shows how new electronic properties emerge when a bulk material is thinned down to a single layer. Other 2D materials include boron nitride, black phosphorous, and transition metal dichalcogenides. Different 2D materials can be assembled one layer at a time into vertically stacked thin films. Such heterostructures can achieve functions and performance not possible with a single material. The interface between different 2D materials is critical to maintaining the unique properties that make them attractive for device applications. The principal investigator will use a newly developed clean-transfer method to prepare 2D heterostructure materials with clean interfaces. A custom-built scanning probe microscope with nanometer-scale light sources at the tip will be used to study the optical and electronic properties of devices with unprecedented resolution. Results from this project will enrich the understanding of these materials and accelerate the development of nanoscale optoelectronics. This interdisciplinary project will integrate research into education of graduate and undergraduate students in material science, engineering, and nanomanufacturing. This project will also seek to broaden participation in science, technology, engineering and mathematics.Technical:This proposal will combine novel 2D-heterostructure material preparation techniques, near-field scanning optics microscopy and near-field scanning photocurrent microscopy to investigate the fundamental optoelectronic properties and photocarrier behaviors in van der Waals material-based heterostructures. The photocurrent imaging with high spatial resolution, below 10nm, can reveal rich physics in nanoscale features. These include local pn-junctions, domain boundaries, edges, dopants, and strains. Imaging such features can significantly improve the understanding and enhance the control of the electronic and photonic properties of this new material system. The objectives of this project are to: (1) demonstrate a prototype tapping-mode near-field scanning photocurrent microscopy to investigate heterostructure devices, (2) improve the spatial resolution of scanning photocurrent imaging technique to sub-10nm level, and (3) study the photoresponsivity of vertically-stacked heterostructures based on graphene, boron nitrides, transmission metal dichalcogenides such as WSe2, MoS2, and MoSe2, and (4) develop fundamental understanding of the roles of nanoscale features, such as edge terminations and interlayer defect formation on the optoelectronic properties.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.