Nanyang Technological University
Interlayer Coupling and Charge Transfer in 2D Semiconductors and Heterostructures
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences
Nanyang Technological University, Singapore
2D semiconductors, such as transitional metal chalcogenides and black phosphorus, have attracted considerable attention due to fascinating physical properties a wide range of applications in valleytronics, optoelectronics and superconductivity. The interlayer interaction is particularly important in both homogenous few-layer systems and heterogeneous structures formed by “lego” fashion, which underpins the foundation for rational engineering towards unprecedented functionality. In this talk, I will introduce our work on interlayer coupling and charge transfer in 2D atomically thin semiconductors and their heterostructures. The unique charge transfer mechanism in 2D semiconductor heterostructures leads to an interesting blinking phenomenon, whereby a bright state emission occurs in one monolayer while a dark state emission occurs in the other, and vice versa. Such correlated blinking can be probed in detail by steady-state and transient spectroscopy measurements, providing new platform to study the long-standing puzzling blinking phenomenon in nanomaterials. In homogenous system, I will present how the charge transfer by a gate modulation breaks the symmetry in a bilayer sample such that a charge-induced second harmonic generation is produced, due to a confined charging in W-atomic plane and a screening effect.
1. W.G. Xu, W.W. Liu, J. F. Schmidt, W.J. Zhao, X. Lu, T. Raab, C. Diederichs, W.B. Gao, D. V. Seletskiy, and Q.H. Xiong*, “Correlated fluorescence blinking in two-dimensional semiconductor heterostructures”, Nature, Doi:10.1038/nature20601 (2017)
2. H.K. Yu, D. Talukdar, W.G. Xu, J.B. Khurgin* and Q.H. Xiong*, "Charge-Induced Second-Harmonic Generation in Bilayer WSe2", Nano Lett.15(8), 5653-5657 (2015)
3. Y.Y. Zhao, X. Luo, H. Li, J. Zhang, P.T. Araujo, C.K. Gan, J. Wu, H. Zhang, S.Y. Quek, M.S. Dresselhaus, and Q.H. Xiong, “Interlayer breathing and shear modes in few-trilayer MoS2 and WSe2”, Nano Lett. 13, 1007-1015 (2013)
Bio: Qihua Xiong received his B.S. degree in physics from Wuhan University in 1997, and then finished three years graduate studies at the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. He went to the United States in 2000 and received his Ph.D. degree under the supervision of Prof. Peter C. Eklund from The Pennsylvania State University in 2006. After three years postdoctoral experience in Prof. Charles M. Lieber’s group at Harvard University, he joined Nanyang Technological University as an assistant professor in 2009. He was promoted to Nanyang Associate Professor with tenure in 2014, and then to full Professor in 2016. He is a Fellow of Singapore National Research Foundation awarded in 2009 and the inaugural NRF Investigatorship Award by Singapore National Research Foundation. He is the recipient of IPS Nanotechnology Physics Award (2015) and Nanyang Award for Research Excellenceof NTU (2014). Prof. Xiong’s research focuses on light-matter interactions of emergent quantum matter by optical spectroscopy approaches. He recently ventured into the field of 2D layered materials and laser cooling of solids.