[CCoE Notice] TcSUH Special Seminar: Microwave Imaging of Edge States and Electrical Inhomogeneity in 2D Materials

[Grayson, Audrey A]

Microwave Imaging of Edge States and Electrical Inhomogeneity in 2D Materials

PROF. Keji Lai

Assistant Professor, Department of Physics

University of Texas at Austin


Wednesday, April 13, 2016

HSC 102  •  10:00 a.m. – 11:00 a.m.



ABSTRACT:
The understanding of various types of disorders in 2D materials, including dangling bonds at the edges, defects in the bulk, and charges in the substrate, is of fundamental importance for their applications in electronics and photonics. Because of the imperfections, electrons moving on the 2D plane experience a spatially non-uniform Coulomb environment, whose effect on the charge transport has not been microscopically probed. Using a non-invasive microwave impedance microscope with ~100nm resolution and ~1nS sensitivity, we can visualize the spatial evolution of the insulator-to-metal transition in monolayer and few-layer MoS2 field-effect transistors. As the transistors are gradually turned on, electrical conduction emerges initially at the edges before appearing in the bulk, which can be explained by first-principles calculations. Strong electrical inhomogeneity is observed in the MIM images, revealing the fluctuations of disorder potential in the 2D sheets. I will also discuss the conductance mapping in ion-gel-gated electric double-layer transistors and 2D devices under laser illumination. The combination of novel FETs and impedance microscopy paves the way to study phase transitions in complex materials induced by electrostatic field effects.
BIO:
Dr. Lai received his undergraduate degree from Tsinghua University, China, and PhD from Princeton University, both in Electrical Engineering. He was the Karel Urbanek Postdoctoral Fellow and the King Abdullah University of Science and Technology Global Research Partnership Postdoctoral Scholar at the Applied Physics Department at Stanford University. After joining UT-Austin in 2012, he was awarded the DOE Early Career Award (2013), the 2015 International Union of Pure and Applied Physics (IUPAP) Young Scientist Prize in Structure and Dynamics of Condensed Matter, and the 2016 Presidential Early Career Awards for Scientists and Engineers (PECASE).


Persons with disabilities who require special accommodations in attending this lecture should call (713) 743-8213.
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