Monolayer transition metal dichalcogenide heterojunctions, including vertical and lateral p–n junctions, have attracted considerable attention due to their potential applications in electronics and optoelectronics. Lattice-misfit strain in atomically abrupt lateral heterojunctions, such as WSe2–MoS2, offers a new band-engineering strategy for tailoring their electronic properties. However, this approach requires an understanding of the strain distribution and its effect on band alignment. Here, we study a WSe2–MoS2 lateral heterojunction using scanning tunnelling microscopy and image its moiré pattern to map the full two-dimensional strain tensor with high spatial resolution. Using scanning tunnelling spectroscopy, we measure both the strain and the band alignment of the WSe2–MoS2 lateral heterojunction. We find that the misfit strain induces type II to type I band alignment transformation. Scanning transmission electron microscopy reveals the dislocations at the interface that partially relieve the strain. Finally, we observe a distinctive electronic structure at the interface due to hetero-bonding.
Subscribe to Journal
Get full journal access for 1 year
only $15.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Mak, K. F., Lee, C., Hone, J., Shan, J. & Heinz, T. F. Atomically thin MoS2: A new direct-gap semiconductor. Phys. Rev. Lett. 105, 136805 (2010).
Splendiani, A. et al. Emerging photoluminescence in monolayer MoS2. Nano Lett. 10, 1271–1275 (2010).
Duan, X. D., Wang, C., Pan, A. L., Yu, R. Q. & Duan, X. F. Two-dimensional transition metal dichalcogenides as atomically thin semiconductors: opportunities and challenges. Chem. Soc. Rev. 44, 8859–8876 (2015).
Liu, G. B., Xiao, D., Yao, Y. G., Xu, X. D. & Yao, W. Electronic structures and theoretical modelling of two-dimensional group-VIB transition metal dichalcogenides. Chem. Soc. Rev. 44, 2643–2663 (2015).
Mak, K. F. & Shan, J. Photonics and optoelectronics of 2D semiconductor transition metal dichalcogenides. Nat. Photon. 10, 216–226 (2016).
Fang, H. et al. Strong interlayer coupling in van der Waals heterostructures built from single-layer chalcogenides. Proc. Natl Acad. Sci. USA 111, 6198–6202 (2014).
Tongay, S. et al. Tuning interlayer coupling in large-area heterostructures with CVD-grown MoS2 and WS2 monolayers. Nano Lett. 14, 3185–3190 (2014).
Hong, X. et al. Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures. Nat. Nanotech. 9, 682–686 (2014).
Chiu, M.-H. et al. Determination of band alignment in the single-layer MoS2/WSe2 heterojunction. Nat. Commun. 6, 7666 (2015).
Wilson, N. R. et al. Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures. Sci. Adv. 3, e1601832 (2017).
Huang, C. et al. Lateral heterojunctions within monolayer MoSe2–WSe2 semiconductors. Nat. Mater. 13, 1096–1101 (2014).
Gong, Y. J. et al. Vertical and in-plane heterostructures from WS2/MoS2 monolayers. Nat. Mater. 13, 1135–1142 (2014).
Duan, X. et al. Lateral epitaxial growth of two-dimensional layered semiconductor heterojunctions. Nat. Nanotech. 9, 1024–1030 (2014).
Li, M.-Y. et al. Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface. Science 349, 524–528 (2015).
Yun, W. S., Han, S. W., Hong, S. C., Kim, I. G. & Lee, J. D. Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te). Phys. Rev. B 85, 033305 (2012).
Johari, P. & Shenoy, V. B. Tuning the electronic properties of semiconducting transitionmetal dichalcogenides by applying mechanical strains. ACS Nano 6, 5449–5456 (2012).
Li, H. et al. Optoelectronic crystal of artificial atoms in strain-textured molybdenum disulphide. Nat. Commun. 6, 7381 (2015).
Shi, H., Pan, H., Zhang, Y. W. & Yakobson, B. I. Quasiparticle band structures and optical properties of strained monolayer MoS2 and WS2. Phys. Rev. B 87, 155304 (2013).
Liu, Z. et al. Strain and structure heterogeneity in MoS2 atomic layers grown by chemical vapour deposition. Nat. Commun. 5, 5246 (2014).
Hui, Y. Y. et al. Exceptional tunability of band energy in a compressively strained trilayer MoS2 sheet. ACS Nano 7, 7126–7131 (2013).
Feng, J., Qian, X., Huang, C.-W. & Li, J. Strain-engineered artificial atom as a broad-spectrum solar energy funnel. Nat. Photon. 6, 866–872 (2012).
He, K., Poole, C., Mak, K. F. & Shan, J. Experimental demonstration of continuous electronic structure tuning via strain in atomically thin MoS2. Nano Lett. 13, 2931–2936 (2013).
Zhu, C. R. et al. Strain tuning of optical emission energy and polarization in monolayer and bilayer MoS2. Phys. Rev. B 88, 121301 (2013).
Rice, C. et al. Raman-scattering measurements and first-principles calculations of strain-induced phonon shifts in monolayer MoS2. Phys. Rev. B 87, 081307 (2013).
Castellanos-Gomez, A. et al. Local strain engineering in atomically thin MoS2. Nano Lett. 13, 5361–5366 (2013).
Conley, H. J. et al. Bandgap engineering of strained monolayer and bilayer MoS2. Nano Lett. 13, 3626–3630 (2013).
Liu, N., Tersoff, J., Baklenov, O., Holmes, A. L. & Shih, C. K. Nonuniform composition profile in In0.5Ga0.5As alloy quantum dots. Phys. Rev. Lett. 84, 334–337 (2000).
Cosma, D. A., Wallbank, J. R., Cheianov, V. & Fal’ko, V. I. Moiré pattern as a magnifying glass for strain and dislocations in van der Waals heterostructures. Faraday Discuss. 173, 137–143 (2014).
Jiang, Y. et al. Visualizing strain-induced pseudomagnetic fields in graphene through an hBN magnifying glass. Nano Lett. 17, 2839–2843 (2017).
Zhang, C. et al. Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS2/WSe2 hetero-bilayers. Sci. Adv. 3, e1601459 (2017).
Goodier, J. N. Concentration of stress around spherical and cylindrical inclusions and flaws. J. Appl. Mech. Trans. ASME 55, 39–44 (1933).
Kang, J., Tongay, S., Zhou, J., Li, J. & Wu, J. Band offsets and heterostructures of two-dimensional semiconductors. Appl. Phys. Lett. 102, 012111 (2013).
Guzman, D. M. & Strachan, A. Role of strain on electronic and mechanical response of semiconducting transition-metal dichalcogenide monolayers: An ab-initio study. J. Appl. Phys. 115, 243701 (2014).
Zhang, C. et al. Probing critical point energies of transition metal dichalcogenides: surprising indirect gap of single layer WSe2. Nano Lett. 15, 6494–6500 (2015).
Park, J. et al. Spatially resolved one-dimensional boundary states in graphene–hexagonal boron nitride planar heterostructures. Nat. Commun. 5, 5403 (2014).
This research was supported with grants from the Welch Foundation (F-1672), the US National Science Foundation (NSF) (DMR-1306878, EFMA-1542747) and the Materials Research Science and Engineering Center (DMR-1720595). L.J.L. acknowledges support from KAUST (Saudi Arabia), MOST and TCECM, Academia Sinica (Taiwan) and AOARD FA23861510001 (USA). C.Z acknowledges support from the National Natural Science Foundation of China (Grant No. 11774268). Y.S.S acknowledges support from the Yan Jici Talent Students Program. This work made use of the electron microscopy facility of the Cornell Center for Materials Research with support from the NSF (DMR-1719875 and DMR-1429155).
The authors declare no competing financial interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Electronic supplementary material
About this article
Cite this article
Zhang, C., Li, M., Tersoff, J. et al. Strain distributions and their influence on electronic structures of WSe2–MoS2 laterally strained heterojunctions. Nature Nanotech 13, 152–158 (2018) doi:10.1038/s41565-017-0022-x
Solid State Communications (2020)
Physica E: Low-dimensional Systems and Nanostructures (2020)
Self-Healing Originated van der Waals Homojunctions with Strong Interlayer Coupling for High-Performance Photodiodes
ACS Nano (2019)
Nature Communications (2019)
Physical Chemistry Chemical Physics (2019)