Quenching the bandgap of two-dimensional semiconductors with a perpendicular electric field

Abstract

Perpendicular electric fields can tune the electronic band structure of atomically thin semiconductors. In bilayer graphene, which is an intrinsic zero-gap semiconductor, a perpendicular electric field opens a finite band gap. So far, however, the same principle could not be applied to control the properties of a broader class of 2D materials, because the required electric fields are beyond reach in current devices. To overcome this limitation, we design double ionic gated transistors that enable the application of large electric fields up to 3 V/nm. Using such devices, we continuously supress the band gap of few-layer semiconducting transition metal dichalcogenides, bilayer to heptalayer WSe 2 , from 1.6 V to zero. Our results illustrate an unprecedented level of control on the band structure of 2D semiconductors.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 [1], however, the small thickness prevents efficient screening, so that a perpendicular electric field uniformly influences the entire system, modifying its band structure [2][3][4][5][6][7][8][9][10][11].Indeed, a zero-gap semiconductor such as bilayer graphene can be turned into a gapped insulator using double-gated transistors to apply a perpendicular electric field [2][3][4]. Despite representing a breakthrough, continuous control of the band structure in transistors has not found widespread use because -as it has become apparent in multiple, recent experiments [7,10,12]-the limited maximum electric field that can be applied in common devices does not allow significant changes to be induced in most 2D materials. Indeed, whereas theory [5, 9], and our own calculations (see Supplementary Note S8), predict that sufficiently strong fields can quench the band gap of few layer semiconductors, earlier works [7,12] have only shown a 10 % gap reduction (or less) at fields reached in conventional double-gated transistors.

Strong gate-tunability of flat bands in bilayer graphene due to moiré encapsulation between hBN monolayers

“…Most recently, ref. 36 and 37 reported realizations of an electric field up to 3.5 V nm −1 across a WSe 2 bilayer using ionic liquid gates, one order of magnitude higher than required in this work. In Fig.…”

Filling the Gap between Heteroatom Doping and Edge Enrichment of 2D Electrocatalysts for Enhanced Hydrogen Evolution

“…Furthermore, according to the previously developed model, , the nanosheet’s Fermi level could be effectively tuned by electrochemical potential during HER. Therefore, we have examined the electronic states of P-MoS 2 during HER via in situ transport measurement. , As shown in the insets in Figure g,h, the threshold voltage ( V T ) of the MoS 2 nanosheet before and after phosphorus doping was evaluated to be 0.53 and 0.1 V (vs reversible hydrogen electrode, RHE), respectively.…”

Two-dimensional Heisenberg models with materials-dependent superexchange interactions

“…Inspired by the high Tc in the 2D magnetic metal Cr 3 Te 6 , we explore the possible high Tc magnetic semiconductors with the same crystal structure of Cr 3 Te 6 by 4(a) and (b), the band gap for 2D Cr 3 O 6 and Mn 3 O 6 is 0.99 eV and 0.75 eV, respectively. When applying an out-of-plane electric field with a range of ± 0.3 V/ Å, which is possible in experiment [49], the band gap of Cr 3 O 6 (Mn 3 O 6 ) increases (decreases) with increasing electric field, as shown in Fig. 4(c).…”