Observation of Strong Interlayer Coupling in MoS₂/WS₂ Heterostructures

Abstract

Epitaxial growth of A-A and A-B stacking MoS2 on WS2 via a two-step chemical vapor deposition method is reported. These epitaxial heterostructures show an atomic clean interface and a strong interlayer coupling, as evidenced by systematic characterization. Low-frequency Raman breathing and shear modes are observed in commensurate stacking bilayers for the first time; these can serve as persuasive fingerprints for interfacial quality and stacking configurations.

Interlayer‐State‐Coupling Dependent Ultrafast Charge Transfer in MoS2/WS2 Bilayers

“…From our calculations ( Table 1 ) and also previous results,22 AB 1 ‐2H, AB 2 ‐2H, and AA 1 ‐3R are the stable configurations with a smaller interlayer spacing of 6.3 Å; while AA 2 ‐3R is metastable with a larger interlayer spacing of 6.8 Å. The formation energies of AB 1 ‐2H, AB 2 ‐2H, and AA 1 ‐3R is of similar strength, but much lower than in AA 2 ‐3R 21. Both AA 2 ‐3R and AB 3 ‐2H share the similar orientation and interlayer distance (6.8 Å) and hole dynamics.…”

“…The MX 2 materials share similar crystalline structures and symmetries, but possess distinct electronic properties in bandgaps, photoabsorption, and spin–orbit coupling strength 7, 8, 9. The heterostructures vertically reassembled from different 2D materials form even richer material systems, and thus provide a new platform for investigating new physics12, 13, 14, 15, 16 and exploring new applications 17, 18, 19, 20, 21, 22, 23, 24. The heterostructures of two MX 2 are of particular interests because many of them form type II heterojunctions,25, 26, 27 which facilitate the efficient separation of photoexcited electrons and holes28, 29 and therefore exhibit great potentials in the applications of photodetectors,30, 31 photovoltaic cells,32, 33 and light emitters 34…”

“…Recently, MX 2 bilayers with defined interlayer geometry can be directly grown by chemical vapor deposition methods in several groups 15, 20, 21. And to utilize the two‐color pump–probe optical technique, the charge transfer lifetime can be obtained by evaluating the rising up part of the pump–probe curve 28, 29.…”

The Effect of Twin Grain Boundary Tuned by Temperature on the Electrical Transport Properties of Monolayer MoS2

“…where σ0 is a fitting parameter, Ea is the activation energy, and kB is Boltzmann constant [34,35]. In contrast with the VRH transport at low temperature, the NNH model at high temperature is reasonable for impeding the electrical transport by twin GB which serves as the line defects, scattering centers for charge carriers that can decrease the conductivity.…”

MoS2/WS2 Heterojunction for Photoelectrochemical Water Oxidation

“…The heterojunction exhibits photocurrent and incident-photon-to-current-efficiencies (IPCE) 10 times 6 higher than the films comprised of the individual constituents. We attribute this to the more efficient exciton dissociation enabled by the creation of atomically thin p-n junctions analogous to MoS 2 /WS 2 bilayer heterostructures grown via CVD, 29,30 which can occur at faster timescales than the charge carriers recombination in individual WS 2 and MoS 2 layers. 31 The charges separated states in the bulk heterojunction have also been predicted to be long-lived despite the close contiguity of electrons and holes, increasing the chance of the water oxidation reaction to occur.…”