Associate Professor of Mechanical Engineering and Materials Science and Engineering
Seminar: Stackable electronics enabled by freestanding 2D/3D materials
Abstract: 2D material-based devices have received great deal of attention as they can be easily stacked to obtain multifunctionality. With their ultrathin thicknesses, such multifunctioning devices become so flexible and conformal that they can be placed onto any 3D featured surfaces. However, 2D heterostructures are typically demonstrated as stacked flakes where single or few devices can be fabricated due to lack of strategies for layer-by-layer stacking of 2D materials at the wafer scale. In this talk, I will discuss about our unique strategy to isolate wafer-scale 2D materials into monolayers and stack them into a heterostructures by using a layer-resolved splitting (LRS) technique . This technique enables my group at MIT to explore unprecedented wafer-scale 2D heterodevices including integrated photonics, 3D neuromorphic computing, and microLEDs, which will be introduced in my talk.
While 2D heterostructures promise interesting futuristic devices, the performance of 2D material-based devices is substantially inferior to that of conventional 3D semiconductor materials. However, 3D materials exist as their bulk form, thus it is challenging to stack them together for heterostructures. Obviously, conformal coating of such single-crystalline bulks on 3D features is impossible. My group at MIT has recently invented a 2D materials-based layer transfer (2DLT) technique that can produce single-crystalline freestanding membranes from any compound materials with their excellent semiconducting performance [2-4]. This technique is based on remote epitaxy of single-crystalline films on graphene followed by peeling from graphene. Stacking of freestanding 3D material membranes will enable unprecedented 3D heterostructures whose performance is expected to be superior to that of 2D heterostructures. I will talk about our group’s effort to apply single-crystalline freestanding membranes for flexible, conformal electronics as well as for 3D heterostructures. Finally, I will conclude my talk by discussing perspectives of coupling 2D-3D freestanding membranes for 2D-3D mixed heterostructured devices that can be enabled by our LRS and 2DLT techniques [5,6].
- J. Shim, S. Bae, et al, and J. Kim, “Controlled crack propagation for atomic precision handling of wafer-scale two-dimensional materials” Science, 362, 665 (2018)
- Y. Kim, et al, and J. Kim, “Remote epitaxy through graphene enables two-dimensional material based layer transfer” Nature, Vol. 544, 340 (2017)
- W. Kong, et al, and J. Kim, “Polarity govern atomic interaction through two-dimensional materials”, Nature Materials, Vol. 17, 999 (2018)
- S. Bae et al, and J. Kim, “Graphene-assisted spontaneous relaxation towards dislocation-free heteroepitaxy”, Nature Nanotechnology (2020)
- S. Bae, et al, and J. Kim, “Integration of bulk materials with two-dimensional materials for physical coupling and applications”, Nature Materials (2019)
- H. Kum, et al., and J. Kim, “Heterogeneous integration of singlecrystalline complex-oxide membranes, Nature, Vol 578, 75-81 (2020)
About the speaker: Jeehwan Kim joined the Mechanical Engineering faculty in September 2015. He joined the Materials Science and Engineering as a joint faculty member in February 2016. Before MIT, Kim was a research staff member at IBM’s T.J. Watson Research Center, conducting research in photovoltaics, 2D materials, graphene, and advanced CMOS devices. He has been named a Master Inventor at IBM for his prolific creativity, with over 100 patent filings in five years. Kim’s breakthrough contributions include: demonstration of peeling of large-area single-crystal graphene grown from a SiC substrate, enabling reuse of the expensive substrate; successful growth of GaN on grapheme, with 25% lattice mismatch and demonstrating that GaN films grown from the process function well as LEDs, pointing to a new principle for growing common semiconductors for flexible electronics; and achieving high efficiency in Si/polymer tandem solar cells and 3D solar cells.
Host: Kysung Lee, assistant professor of electrical and computer engineering and materials science and engineering.