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Vertical and in-plane heterostructures from WS2/MoS2 monolayers

Abstract

Layer-by-layer stacking or lateral interfacing of atomic monolayers has opened up unprecedented opportunities to engineer two-dimensional heteromaterials. Fabrication of such artificial heterostructures with atomically clean and sharp interfaces, however, is challenging. Here, we report a one-step growth strategy for the creation of high-quality vertically stacked as well as in-plane interconnected heterostructures of WS2/MoS2 via control of the growth temperature. Vertically stacked bilayers with WS2 epitaxially grown on top of the MoS2 monolayer are formed with preferred stacking order at high temperature. A strong interlayer excitonic transition is observed due to the type II band alignment and to the clean interface of these bilayers. Vapour growth at low temperature, on the other hand, leads to lateral epitaxy of WS2 on MoS2 edges, creating seamless and atomically sharp in-plane heterostructures that generate strong localized photoluminescence enhancement and intrinsic p–n junctions. The fabrication of heterostructures from monolayers, using simple and scalable growth, paves the way for the creation of unprecedented two-dimensional materials with exciting properties.

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Figure 1: Schematic of the synthesis and the overall morphologies of the vertically stacked and in-plane WS2/MoS2 heterostructures.
Figure 2: STEM Z-contrast imaging and elemental mapping of the stacked WS2/MoS2 heterostructures.
Figure 3: Raman and PL characterization of the WS2/MoS2 vertical heterostructure.
Figure 4: Atomic structure of the lateral heterojunctions between WS2 and MoS2 monolayers.
Figure 5: Raman and PL characterizations of in-plane WS2/MoS2 heterojunction.

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Acknowledgements

We thank A. Lupini for providing the script for STEM image quantification. This work was supported by the Army Research Office MURI grant W911NF-11-1-0362, US DOE grant DE-FG02-09ER46554 (J.L., S.T.P.), a Wigner Fellowship through the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC, for the US DOE (W.Z.), the FAME Center, one of six centres of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA, the US Office of Naval Research MURI grant N000014-09-1-1066, NSF grant ECCS-1327093 and MOE Academic Research Fund (AcRF) Tier 1 RG81/12 project Singapore and Si-COE project, Singapore. This research was also supported through a user project supported by ORNL’s Center for Nanophase Materials Sciences (CNMS), which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US DOE. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy under Contract No. DE-AC02-05CH11231. This work was also supported by the Singapore National Research Foundation under NRF RF Award No. NRF-RF2013-08, the start-up funding from Nanyang Technological University (M4081137.070).

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Y.G., J.L. and X.W. contributed equally to this work. Y.G. designed the growth procedures and carried out part of the characterization. Y.G., X.W. and G.Y. worked on the growth. W.Z. and J.L. carried out STEM experiments. G.S. and S.L. made the FET devices and carried out the electrical measurement. Z.L. performed part of the Raman and PL characterization. H.T., X.Z. and J.L. carried out DFT calculations. Y.G., J.L., X.W., W.Z., Z.L., G.S., S.L., M.T., H.T. and P.M.A. analysed the results and co-wrote the paper. All authors participated in discussions.

Corresponding authors

Correspondence to Wu Zhou or Pulickel M. Ajayan.

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The authors declare no competing financial interests.

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Gong, Y., Lin, J., Wang, X. et al. Vertical and in-plane heterostructures from WS2/MoS2 monolayers. Nature Mater 13, 1135–1142 (2014). https://doi.org/10.1038/nmat4091

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