March 21
@
12:20 PM
–
1:20 PM
Materials Science Seminar Series presents Professor Joan Redwing on Thursday, March 21, from 12:20 to 1:20 p.m. The seminar is hosted by Professor Jason Kawasaki and will be held in MS&E building room 265. Professor Redwing will be discussing epitaxial growth of transition metal dichalcogenides – an enabling technology for large area 2D devices.
Abstract
Monolayer and few-layer semiconducting Transition Metal Dichalcogenides (TMDs), exemplified by materials like MoS2 and WSe2, have garnered increasing interest for next-generation electronics such as gate-all-around nanosheet transistors, neuromorphic devices and sensors/imagers heterogeneously integrated with silicon CMOS technology. The interest in semiconducting TMDs arises from their atomically thin nature and passivated van der Waals surfaces, however, realization of high-performance devices requires advances in TMD synthesis to provide wafer-scale films that can be readily integrated into devices via either direct growth or layer transfer methods.
Our work has focused on the development of metalorganic chemical vapor deposition (MOCVD) as a manufacturing-compatible approach for wafer-scale semiconducting TMDs. The TMDs are grown epitaxially on 2” diameter c-plane sapphire by MOCVD at elevated temperatures (>800 °C) to obtain high crystal quality. Nucleation of TMDs on sapphire is intimately tied to the surface structure and the growth chemistry which can be controlled to achieve unidirectional TMD domains with a significant reduction in mirror twin domains in coalesced films. In situ spectroscopic ellipsometry is demonstrated to be an effective real-time monitor of TMD growth even at the sub-monolayer level which can be exploited to track surface coverage as a function of time under varying growth conditions. The ability to precisely control and modulate precursor flux during growth is used to synthesize in-plane heterostructures that enable localized exciton confinement and emission. Applications for wafer-scale TMD monolayers in nanoelectronics, sensing, and photonics will be discussed.
Bio
Joan Redwing is a Distinguished Professor of Materials Science and Engineering and Electrical Engineering at Penn State University. She received her Ph.D. in Chemical Engineering from the University of Wisconsin-Madison in 1994 under the direction of Prof. Thomas Kuech. She currently serves as Director of the 2D Crystal Consortium, an NSF Materials Innovation Platform (MIP) national user facility that is focused on the synthesis and characterization of 2D materials for next-generation devices. Her research focuses on crystal growth and epitaxy of electronic materials, with an emphasis on thin film and nanomaterial synthesis by metalorganic chemical vapor deposition. She is a fellow of the Materials Research Society, the American Physical Society, and the American Association for the Advancement of Science. She is an author on over 300 publications in refereed journals and holds 8 U.S. patents.
Materials Science Seminar Series – Speaker Professor Joan Redwing