Abstract
Monolayer MX2 (M = Mo, W; X = S, Se) has recently been drawn much attention due to their application possibility as well as the novel valley physics. On the other hand, it is also important to understand the electronic structures of bulk MX2 for material applications since it is very challenging to grow large size uniform and sustainable monolayer MX2. We performed angle-resolved photoemission spectroscopy and tight binding calculations to investigate the electronic structures of bulk 2H-MX2. We could extract all the important electronic band parameters for bulk 2H-MX2, including the band gap, direct band gap size at K (-K) point and spin splitting size. Upon comparing the parameters for bulk 2H-MX2 (our work) with mono- and multi-layer MX2 (published), we found that stacked layers, substrates for thin films, and carrier concentration significantly affect the parameters, especially the band gap size. The origin of such effect is discussed in terms of the screening effect.
Highlights
Monolayer MX2 (M = Mo, W; X = S, Se) has recently been drawn much attention due to their application possibility as well as the novel valley physics
We will try to show that the band dispersion of bulk MX2 near the in-plane K point can be described within the model
Note that while the inversion symmetry is restored in the bulk and the valley physics is removed, the characteristics of the monolayer such as the spin band splitting remains in the dispersion at the K point
Summary
Among the TMDs, the group 6 TMDs, MX2 (M =Mo, W; X =S, Se), exhibit interesting electronic properties such as indirect (bulk) to direct (monolayer) band gap transition[6,7], valley degeneracy[9] and spin-orbit interaction (SOI) induced spin band splitting at the K and -K points of the hexagonal Brillouin zone[10]. Exploiting these fundamental electronic properties, the valley degeneracy could be lifted by using circularly polarized light[11,12,13,14,15] and valley Hall effect was observed in monolayer MX216–18. These results show that the massive Dirac fermion parameters for monolayer MX2 can be affected www.nature.com/scientificreports/
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call