Closing the band gap in 2D semiconductors
Relativistic periodic DFT calculations show that the band gap of single-layer transition-metal dichalcogenides (MoWSeS) are reduced by high external electric fields. MoS2 and MoSe2 become metallic at fields of 6.5 V Å−1 and 4.5 V Å−1.
With proper 2D periodic boundary conditions in BAND, a homogeneous electric field can be applied, polarizing the monolayers and reducing the band gap.
The band gaps of MoWSeS monolayers are unaffected by field strengths upto 2 V Å−1(left). 2D periodic boundary conditions, without artificial repetition of the surface in the third dimension, allows for proper polarization across the MoS2 surface (right).