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Public Seminar of PhD Candidate:
Scanning Tunneling Microscopic Study Of Defects And Heterointerfaces Of Transition Metal Dichalcogenides

Speaker:Ms. Mengfei YUAN
Affiliation:The University of Hong Kong
Date:June 7, 2023 (Wednesday)
Time:2:30 p.m.
Venue:Room 518, 5/F, Chong Yuet Ming Physics Building, The University of Hong Kong


Transition-metal dichalcogenides (TMDs) are important family of two-dimensional (2D) materials that possess many unique electronic and optoelectronic properties with great application potentials. On the other hand, epitaxial TMD films often contain various defects, such as mirror-twin domain boundaries (MTBs) that will bring in new effects. An important one is the band-bending caused by the MTBs, which has been ascribed to a charging effect. In this talk, experiments on band-bending of monolayer MoSe2 in the vicinity of MTBs studied by scanning tunneling microscopy/spectroscopy (STM/STS) will be presented. In particular, the effects of substrates and defect geometry on band-bending are unveiled, which are accounted for by the static charge model. 
Besides MTBs, doping of Nb and Re atoms in MoSe2 is conducted by molecular beam epitaxy (MBE) and characterized by a combination of STM and scanning transmission electron microscopy (STEM) techniques. It is shown that Nb and Re are shallow dopants (Nb is an acceptor while Re a donor). In addition, characteristics of NbSe2/MoSe2 and ReSe2/MoSe2 heterointerfaces are probed. Finally, post-deposition of In on MoSe2 has led to the formation of In2Se3 with various phases. 

Anyone interested is welcome to attend.