Speaker: Dr. Yutsung Tsai
Affiliation: Center for Complex Quantum Systems in University of Texas, Austin
Host: Associate Professor Shaffique Adam
Abstract Details: Heterostructures are artificially engineered systems that consist of two or more dissimilar semiconductor junctions. Scientists have developed many combinations of heterostructures like Si/SiGe, GaAs/AlGaAs, ZnS/CdSe, and HgTe/CdTe for high-speed electronic and optoelectronic devices by tailoring those vertical multijunctions through quantum confinement. In recent years, the emergence of transition metal dichalcogenides (TMDs) has opened new frontiers in heterostructure research. In particular, their monolayer form not only enables optoelectronic application with their direct-gap band structure, but also provides a myriad of possibilities through vertical stacking due to their van der Waals (vdW) interactions between layers. On the other hand, although vertically stacked TMDs optoelectronic heterostructures have been demonstrated extensively, atomically-thin two-dimensional (2D) TMDs lateral multijunctions beyond two heterojunctions have only been explored sparingly; this has limited the development of 2D optoelectronics.
In this talk, I would like to present recently achieved lateral 2D TMDs multijunctions about the growing method, their heterostructures, optoelectronic properties, and the photo-generated carrier transport mechanism. My motivation of developing these multijunctions as nano-optoelectronic platforms for quantum information, photovoltaics, and light-induced superconductivity will then be revealed and discussed. This critical development will be the building block for more advanced 2D optoelectronic architecture.
About the Speaker: Dr. Yutsung Tsai received his PhD in Physics from the State University of New York at Buffalo in 2015 and have been working as a postdoctoral research fellow at the Center for Complex Quantum Systems in University of Texas at Austin for the past two years. He has participated in condensed matter experimental research in seven labs since his undergraduate training and become a believer for “better collaboration makes better research.” The PhD students and undergraduate students mentored by him advocated his devotion by acquiring advanced experimental skills like atomic force microscopy, micro-Raman compact mapping and appearing as first authors of publications on Nature Nanotechnology.
His current professional interests focus on optoelectronic semiconductors, particularly two-dimensional transition metal dichalcogenides (2D TMDs) lateral multijunctions MX2/M’X’2/MX2 (M=W, Mo; X=S, Se) for photovoltaic applications. He recently observed photo-generated carriers trapped by nanoscale quantum confined structures that was manifested by 100-fold photoconductivity at M’X’2 junction. This discovery enables innovative technology, for example, harvesting these trapped photo-generated carriers for solar cell use.