Bandstructure modulation of two-dimensional WSe2 by electric field

Abstract

By means of density functional theory computations, we study band-gap tuning in multi-layer WSe2 sheets by external electric fields. It shows that the fundamental band gap of WSe2 film continuously decreases with an increasing vertical electric field, eventually rendering them metallic. The critical electric fields, at which the semiconductor-to-metal transition occurs, are predicted to be in the range of 0.6–2 V/nm depending on the number of layers. This gap-tuning effect yields a robust relationship, which is essentially characterized by the giant Stark effect (GSE) coefficient S, for the rate of change of band gap with applied external field. The GSE coefficient S is proportional to the number of layers and it can be expressed as (n − 1)c/2.

Signature of Spin-Resolved Quantum Point Contact in p-Type Trilayer WSe2 van der Waals Heterostructure

“…Additionally, the strong perpendicular electric field D, where D = (εTGVTG/dTG − εSGVSG/dSG)/2 where εTG (εSG) is dielectric constant of the top and the bottom hBN and dTG (dSG) is thickness of the top and the bottom hBN, lifts the band edge of at the K point, [34][35][36] and the Γ-K transition can be observed which is also confirmed by our DFT calculations (See S5 for details). Looking at the K point maxima of the valence band under D field, the spin-polarized bands along a perpendicular direction are still existing even under D field and the energy split becomes more resolved.…”

Quenching the band gap of 2D semiconductors with a perpendicular electric field

“…That is because the concomitant application of large positive V IL and large negative V BG also generates a perpendicular electric field that quenches the band gap, in agreement with previous theoretical calculations [5,9] and our own (see Fig. 1D and 1E and Supplementary Note S7).…”

“…An electric field applied perpendicular to the surface of a bulk semiconductor is screened over a finite length, leaving the material interior unaffected. In atomically thin semiconductors [4], however, the small thickness prevents efficient screening, so that a perpendicular electric field uniformly influences the entire system, modifying its band structure [5][6][7][8][9][10][11].…”

Band structure and giant Stark effect in two-dimensional transition-metal dichalcogenides

“…Molybdenum-and tungsten-based dichalcogenides have been intensively investigated. The band gap variation of a few layers of these materials under electric field have been widely studied [24,[53][54][55][56][57][58][59]. Lebègue et al [60] have reported 2D materials by data filtering from their known bulk structures.…”