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