Abstract
Transition metal dichalcogensides (TMDs) such as MX2 (M=Mo or W; X=S or Se) have recently draw a lot of attention, since (1) TMD monolayer has massive Dirac-Fermion with band gap, whereas graphene has no band gap, (2) valley polarization of electron state in TMD monolayer is optically controllable. Out of these intriguing properties, many potential applications have been proposed including nano-electronics, valleytronics and optoelectronics. On the way to the applications, it is necessary to understand basic electronics structures of MX2 quantitatively.
In first part of the talk, electronic structures of MX2 (M=Mo or W; X=S or Se) measured in momentum and energy space, by angle-resolved photoemission spectroscopy (ARPES) will be presented [1]. In comparison between ARPES data and massive Dirac-Fermion model, the important parameters describing low-energy electron physics could be extracted. It will be shown how the parameters evolve by varying chemical composition of MX2 (M=Mo or W; X=S or Se) and its physical origin will also be discussed. In second part of the talk, electronic structure of hydric-treated bulk-MoS2 will be presented [2]. Quantum confined nature of electrons is discovered in the material, indicating reduction of electronic dimensionality from 3D to 2D. Other aspects of the material such as defect states will be discussed. Throughout the talk, it will be emphasized that ARPES is an important tool not only to investigate the basic electronic structure of TMDs but also to find novel electronic nature of TMDs.
[1] B. S. Kim et al., in preparation.
[2] S. H. Cho, B. S. Kim et al., in preparation.
Coffee and tea will be served 20 minutes prior to the seminar.
Anyone interested is welcome to attend.