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Towards High Resolution Time-resolved Imaging to 2D Materials using Low Energy Electrons
Speaker Dr. Changxi Zheng, Monash University
Date 28 September 2017 (Thursday)
Time 11:00 - 12:00
Venue Room 5508 (Lifts 25-26), HKUST

Starting with the discovery of graphene, a large number of van der Waals (vdW) layered materials including semimetals, semiconductors, superconductors, topological insulators and ferromagnetic materials have been intensively investigated globally. These materials not only demonstrate huge potential for future low energy electronics, but also provide a platform to explore exotic physics such as massless Dirac fermions, the valley degree of freedom, topologically protected edge states, and magnetism in two-dimensions. In this talk, I will present a different angle of exploring material growth dynamics and electronic structure of these emerging materials using low energy electrons. Starting with the basics of low energy electron microscopy (LEEM) for the real-time imaging of materials’ surfaces in real and momentum space, I will introduce an example of its powerful applications–our recent discovery of the first vdW material showing room-temperature in-plane ferroelectricity using LEEM. Owing to the strong interaction between low energy electrons and the material’s surface, LEEM and the complementary photoemission electron microscopy (PEEM) can efficiently measure the surface band structure and plasmon dispersion. Finally, I will discuss our current endeavour to develop the first spatially-, time- and spin-resolved LEEM and show how such unique instrument will enable novel capabilities to study fundamental physics.



Changxi Zheng is an Australian Research Council (ARC) DECRA Fellow at The Monash Centre for Atomically Thin Materials, School of Physics & Astronomy, and at the Department of Civil Engineering, Monash University, Australia. Zheng received his PhD in Condensed Matter Physics from Monash University in 2013, working on the development of a worldwide unique III-V low energy electron microscope (LEEM). His major contributions include the discovery of a Ga-rich phase of GaAs(001) and the growth mechanism of GaAs quantum rings. After his PhD, Zheng commenced research on 2D materials, working with Prof. Michael S. Fuhrer group at Monash University. Following the successful award of a DECRA fellowship, in 2014, Zheng supported his own research on a wide range of topics, including 2D materials, optoelectronics, LEEM, time-resolved electron microscopy, molecular beam epitaxy, and high-resolution chemical imaging of cement and biological particles. Zheng is currently developing ultrafast LEEM in collaboration with the Electron Microscopy Center, Chongqing University, China, where he holds a position as visiting scientist.