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Inter-layer coupling and thermal conduction in 2D semiconductors

Speaker: 
Junqiao Wu (University of California, Berkeley)
Date: 
Wed, 10/09/2014 - 11:00am to 12:00pm
Location: 
S16-06 (Graphene Theory Common Seminar Room)
Host: 
Graphene Research Centre
Event Type: 
Seminars

Abstract

Semiconducting two-dimensional (2D) materials have become a focus of research in recent years. One of the unique properties of these materials is the sensitivity of their electronic structure and vibrational spectrum to inter-layer coupling, despite the weak van der Waals interaction between neighboring layers. In this talk, I will discuss our research in controlling inter-layer coupling in homo- and hetero-structures of 2D semiconductors by physical means. We demonstrated that the inter-layer coupling and the resultant physical properties can be modulated thermally and mechanically, and is sensitive to in-plane crystal structure. We employ a diamond anvil cell to apply high hydrostatic pressures onto 2D structures up to 20 GPa, and probe the resultant optical reflection, absorption and emission and Raman spectrum. In addition, we develop a method to measure thermal conduction along different in-plane directions in 2D materials, from which we probe the anisotropy of lattice thermal conductivity and electrical conductivity.

Speaker's bio

Professor Junqiao Wu received a B.S. from Fudan University and a M.S. from Peking University, China, both in physics. He obtained a Ph.D. degree in applied physics from the University of California, Berkeley for work on nitride semiconductors and highly mismatched semiconductor alloys. He did postdoctoral research in the Department of Chemistry at Harvard University on phase transitions in transition metal oxide nanomaterials. He began his faculty appointment in the Department of Materials Science and Engineering at the University of California, Berkeley in 2006. His honors include the Berkeley Fellowship, the 29th Ross N. Tucker Memorial Award, the Berkeley Presidential Chair Fellowship, the U.S. NSF Career Award, the U.S. DOE Early Career Award, and the U.S. Presidential Early Career Award for Scientists and Engineers (PECASE). He has published more than 100 widely cited papers. The Wu group explores novel properties and applications of strongly correlated electron materials with reduced dimensions, phase transitions at the nanoscale, and optoelectronic, thermal and thermoelectric properties of semiconductor alloys and interfaces. More information can be found at http://mse.berkeley.edu/~jwu

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