A STM Study of Epitaxial Monolayer Transition-Metal Dichalcogenides – Line and Point Defects and some Associated Effects

Speaker:Prof.XIE Maohai,The University of Hong Kong

Sponsor:Prof.Ding Sunan

Time:4:00p.m.Tuesday,May 23rd

Place:A718,SINANO

Abstract:
In this talk,He shall describe some of their latest efforts of molecular-beam epitaxy (MBE) of monolayer thin MoSe₂, WSe₂ and MoTe₂. Attention will be paid on the line and point defects in these materials as studied by scanning tunneling microscopy and spectroscopy (STM/S). Inversion domain boundary defects arranged in triangular networks are persistent in as-grown molybdenum-dichalcogenides (MoSe₂ and MoTe₂), which give rise to metallic states confined in one-dimension. He shall present experimental evidences of both quantum confinement and moiré potentialinduced effects on such metallic states. For point defects, such as that in monolayer WSe₂, quasi-particle interference signifying spin-conserving inter-valley scattering is observed, which affirms the strong spin-valley coupling and large spin-splitting at the Q valleys in monolayer WSe₂. Tip induced band-bending effect on defect charge state transition is picked up, allowing one to evaluate the dielectric property of the films. Finally, phase tuning of epitaxial MoTe₂ is demonstrated. The latter would make it attractive for phase-change electronic applications.