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

San Francisco State University, San Francisco CA

Investigators

Abstract

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