报告时间：2017年9月27日10：30

报告地点：科技创新大楼B113

报告题目：Probing Intrinsic and Extrinsic Light Emission in Two-Dimensional Transition Metal Dichalcogenides

Abstract: Two-dimensional (2D) semiconductors, such as transitional-metal-dichalcogenide (TMD) monolayers, have aroused great attention. Even though considerable progress has been achieved recently, intrinsic and extrinsic excitonic states of TMD monolayers are still under discussion and require direct experimental exploration. Here, we report observations of unconventional excitonic emission states of monolayer TMDs under electrical doping and photoexcitation at low temperature. Particularly, the superlinear emission and the unusual linear polarization behaviour of its photon energy opposite to that of exciton emission have been clearly observed, which is assigned to the presence of biexciton states, evidencing the strong Coulomb interactions in such 2D semiconductors. Extrinsic emission bands in monolayer TMDs have also been revealed and attributed to specific localized states resulting from impurities and structural defects, where the exact origin of such states has been discussed. In view of applications, we have developed a highly practical strategy to electrically manipulate the diverse excitonic emission in atomically thin semiconductors, which opens up many possibilities for design and improvement of 2D TMD-based optoelectronic devices.

Biography: Ting YU received his PhD in Department of Physics, National University of Singapore in 2003 and is currently a Professor in Division of Physics and Applied Physics, Nanyang Technological University, Singapore. Dr. YU has received many prestigious awards including Nanyang Excellence Award for Research and Innovation (2008), National Young Scientist Award, National Research Foundation Fellowship Award (2009), Outstanding Young Scientist for the 3rd Inter Academy Panel/World Economic Forum (Summer Davos Forum) ((IAP/WEF, Representative of Singapore, 2010) and Institute of Physics Singapore, Nanotechnology award (2011). His research interests cover fabrication of low dimensional, especially 2D materials and investigation of their optical, optoelectrical and eletrochemical properties for developing novel electronics, optoelectronics and energy conversion/storage. Dr Yu has published more than 230 SCI papers and received over 14,500 nonself-citations. His H-index is 66.

Prof. Ting YU (Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore)