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A dielectric-defined lateral heterojunction in a monolayer semiconductor

Abstract

Owing to their low dimensionality, two-dimensional semiconductors, such as monolayer molybdenum disulfide, have a range of properties that make them valuable in the development of nanoelectronics. For example, the electronic bandgap of these semiconductors is not an intrinsic physical parameter and can be engineered by manipulating the dielectric environment around the monolayer. Here we show that this dielectric-dependent electronic bandgap can be used to engineer a lateral heterojunction within a homogeneous MoS2 monolayer. We visualize the heterostructure with Kelvin probe force microscopy and examine its influence on electrical transport experimentally and theoretically. We observe a lateral heterojunction with an approximately 90 meV band offset due to the differing degrees of bandgap renormalization of monolayer MoS2 when it is placed on a substrate in which one segment is made from an amorphous fluoropolymer (Cytop) and another segment is made of hexagonal boron nitride. This heterostructure leads to a diode-like electrical transport with a strong asymmetric behaviour.

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Acknowledgements

We thank M. Asta, J. Yao and S. Kahn for helpful discussions. This work was primarily supported by the Center for Computational Study of Excited State Phenomena in Energy Materials, which is funded by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division under Contract No. DE-AC02-05CH11231, as part of the Computational Materials Sciences Program. The device fabrication is supported by the National Science Foundation EFRI Program (EFMA-1542741). This research used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under Contract No. DE-AC02-05CH11231, and the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1548562. H.K. was supported by the Deutsche Forschungsgemeinschaft (KL 2961/1-1). C.S.O. acknowledges support from the Singapore National Research Foundation (Clean Energy) PhD Scholarship. R.K. was supported by the JSPS Overseas Research Fellowship Program. S.T. acknowledges support from a NSF DMR 1552220 NSF CAREER award. Growth of hexagonal boron nitride crystals was supported by the Elemental Strategy Initiative conducted by the MEXT, Japan and a Grant-in-Aid for Scientific Research on Innovative Areas ‘Science of Atomic Layers’ from JSPS.

Author information

F.W., M.I.B.U. and H.K. conceived the project and designed the experiments. M.I.B.U. and H.K. performed sample preparation, device fabrication, electrical transport measurements and data analysis. W.Z., M.I.B.U. and S.W. performed KPFM measurements. M.I.B.U. conducted optical spectroscopy. R.K., S.Z. and A.Z. contributed to the device fabrication process. F.W., M.I.B.U. and H.K. simulated the energy band diagram of the heterojunction. C.S.O., F.H.d.J. and D.Y.Q. performed GW calculations on and, together with S.G.L., did the analyses of the quasiparticle band structures. H.C., H.L. and S.T. grew the MoS2 single crystal. K.W. and T.T. grew the hBN single crystal. F.W., S.G.L. and A.Z. supervised the project.

Competing interests

The authors declare no competing interests.

Correspondence to Feng Wang.

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Supplementary Notes 1–4 and Supplementary Figures 1–10

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Further reading

Fig. 1: Engineering 2D heterojunctions through dielectric-dependent bandgap renormalization.
Fig. 2: Current–voltage characteristics of a MoS2 heterojunction device.
Fig. 3: KPFM characterization of the MoS2 heterojunction formation from differences in the degree of local dielectric screening.
Fig. 4: Simulation results of the energy band bending at the 2D heterojunction.