Control of interlayer physics in 2H transition metal dichalcogenides

Abstract

It is assessed in detail both experimentally and theoretically how the interlayer coupling of transition metal dichalcogenides controls the electronic properties of the respective devices. Gated transition metal dichalcogenide structures show electrons and holes to either localize in individual monolayers, or delocalize beyond multiple layers -depending on the balance between spin-orbit interaction and interlayer hopping. This balance depends on layer thickness, momentum space symmetry points and applied gate fields. The design range of this balance, the effective Fermi levels and all relevant effective masses is analyzed in great detail. A good quantitative agreement of predictions and measurements of the quantum confined Stark effect in gated MoS2 systems unveils intralayer excitons as major source for the observed photoluminesence.

Interlayer hybridization and moiré superlattice minibands for electrons and excitons in heterobilayers of transition-metal dichalcogenides

“…11-14 show that P-and AP-type MoTe 2 /MoSe 2 and MoSe 2 /WS 2 heterostructures are type II semiconductors, with a γ-κ indirect band gap. However, it is possible to reduce the offset between the conduction band edges by application of a positive interlayer bias voltage [51][52][53] gates. The resulting potential gradient along the heterostructure's out-of-plane axis will lower the MX 2 (bottom) layer's c band while raising the M X 2 (top) layer's c band, such that a suitable value of V B can impose a degeneracy between the two minima at γ and κ.…”

Electrochemical kinetics as a function of transition metal dichalcogenide thickness

“…The electronic band structure of TMDCs depends on the number of stacked layers [54][55][56]. The band gap of MoS2, MoSe2, WS2, and WSe2 increases with the decreasing layer number (<5L) due to strong quantum confinement in thin layers [56,57].…”

Thickness-Dependent Study of High- Performance WS2-FETs With Ultrascaled Channel Lengths

“…Therefore, in the following discussion, any observed change of R C with T CH is not attributed to a change in SBH for electrons, considering n-FET operation for WS 2 devices. Considering the above statements and assuming a similar effective mass for all multilayer WS 2 channels [44], the efficiency of contact gating through the layered-structure then becomes the dominant factor for R C . This statement is supported by our experimental output characteristics as a function of T CH .…”