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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.