monolayer structure
Arror Li
Contents
•
Crystal structure
•
Band-edge forming and Band structure
•
Direct and Indirect excitation
•
Spin-valley coupling
•
Experimental techniques
Crystal structure
•
Transition metals from
group VI and chalcogens
•
The layer of transition
metal atoms is sandwiched
between two layers of
chalcogens.[1]
•
The layers are weakly
held together by van der
Waals forces
The chalcogen atoms (X) are yellow
and the metal atoms (T) are blue [1]
•
Time-reversal symmetry
•
Space-inversion symmertry
•
In a system with both symmertries,their effect
would typically vanish
• Band
Categorizing
With the standard of orbital(atom)
E(dxy,dx2-y2)
2
E’( dxz, dyz )
1
A1（dz2）
0
Band structure
•
The conduction band-edge state A1（dz2）
•
The valence band-edge state E (dxy,dx2-y2)
Direct excitation(blue)
Indirect excitation(red)
[1]
The red and blue colors refers to the two
inequivalent valleys.
[1]
At the K+ valley, the spin-down and spin-up holes
occupy the (A) and (B) bands, respectively;
while at the K− valley the spin occupation is opposite.
Experimental
techniques
•
Optical microscopy
•
Atomic force microscopy (AFM)
•
μ-Raman spectroscopy
•
μ-PL specctroscopy
Optical microscopy
Atomic force microscopy
(AFM)
a single layer of MoS2 deposited on a silicon
substrate with an oxide layer
μ-Raman spectroscopy
μ-PL specctroscopy
Prospect
•
Electronic device
•
Optical device
•
Catalyze and energy
Remaining problems：production and process
Bibliography
•
[1] Anatolie Mitioglu-Probing the electronic properties of bulk and
monolayer crystals of tungsten dichalcogenides using magneto-spectroscopy
•
[2]CoupledspinandvalleyphysicsinmonolayersofMoS2 andothergroupVidichalcogenides Di Xiao,1,∗ Gui-Bin Liu,2 Wanxiang Feng,1,3,4
Xiaodong Xu,5,6 and Wang Yao2,†
Thanks