Tailoring the dielectric screening in WS2–graphene heterostructures
Source abstract
Abstract
Abstract The environment contributes to the screening of Coulomb interactions in two-dimensional semiconductors. This can potentially be exploited to tailor material properties as well as for sensing applications. Here, we investigate the tuning of the band gap and the exciton binding energy in the two-dimensional semiconductor WS2 via the external dielectric screening. Embedding WS2 in van der Waals heterostructures with graphene and hBN spacers of thicknesses between one and 16 atomic layers, we experimentally determine both energies as a function of the WS2-to-graphene interlayer distance and the charge carrier density in graphene. We find that the modification to the band gap as well as the exciton binding energy are well described by a one-over-distance dependence, with a significant effect remaining at several nanometers distance, at which the two layers are electrically well isolated. This observation is explained by a screening arising from an image charge induced by the graphene layer. Furthermore, we find that the effectiveness of graphene in screening Coulomb interactions in nearby WS2 depends on its doping level and can therefore be controlled via the electric field effect. We determine that, at room temperature, it is modified by approximately 20% for charge carrier densities of 2 × 1012 cm−2.
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Research context
OpenAlex topics: 2D Materials and Applications · Graphene research and applications · Quantum and electron transport phenomena
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References (52)
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1. Ajayi, O. A., Ardelean, J. V., Shepard, G. D., Wang, J. & Antony, A. Approaching the intrinsic photoluminescence linewidth in transition metal dichalcogenide monolayers. 2D Mater. 4, 031011 (2017).10.1088/2053-1583/aa6aa1 ↗
2. Cadiz, F. et al. Excitonic linewidth approaching the homogeneous limit in MoS2-based van der Waals heterostructures. Phys. Rev. X 7, 021026 (2017).
3. Raja, A. et al. Dielectric disorder in two-dimensional materials. Nat. Nanotechnol. 14, 832–837 (2019).10.1038/s41565-019-0520-0 ↗
4. 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).10.1073/pnas.1405435111 ↗
5. Ceballos, F., Bellus, M. Z., Chiu, H. Y. & Zhao, H. Ultrafast charge separation and indirect exciton formation in a MoS2-MoSe2 van der Waals heterostructure. ACS Nano 8, 12717–12724 (2014).10.1021/nn505736z ↗
6. Raja, A. et al. Coulomb engineering of the bandgap and excitons in two-dimensional materials. Nat. Commun. 8, 15251 (2017).10.1038/ncomms15251 ↗
7. Ersfeld, M. et al. Unveiling valley lifetimes of free charge carriers in monolayer WSe2. Nano Lett. 20, 3147–3154 (2020).10.1021/acs.nanolett.9b05138 ↗
8. Wilson, N. R. et al. Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures. Sci. Adv. 3, 1601832 (2017).10.1126/sciadv.1601832 ↗
9. Wu, F., Lovorn, T., Tutuc, E., Martin, I. & Macdonald, A. H. Topological insulators in twisted transition metal dichalcogenide homobilayers. Phys. Rev. Lett. 122, 086402 (2019).10.1103/PhysRevLett.122.086402 ↗
10. Seyler, K. L. et al. Signatures of moiré-trapped valley excitons in MoSe2/WSe2 heterobilayers. Nature 567, 66–70 (2019).10.1038/s41586-019-0957-1 ↗
11. Chernikov, A. et al. Exciton binding energy and nonhydrogenic Rydberg series in monolayer WS2. Phys. Rev. Lett. 113, 076802 (2014).10.1103/PhysRevLett.113.076802 ↗
12. Stier, A. V., Wilson, N. P., Clark, G., Xu, X. & Crooker, S. A. Probing the influence of dielectric environment on excitons in monolayer WSe2: insight from high magnetic fields. Nano Lett. 16, 7054–7060 (2016).10.1021/acs.nanolett.6b03276 ↗
13. Latini, S., Olsen, T. & Thygesen, K. S. Excitons in van der Waals heterostructures: the important role of dielectric screening. Phys. Rev. B 92, 245123 (2015).10.1103/PhysRevB.92.245123 ↗
14. Rösner, M. et al. Two-dimensional heterojunctions from nonlocal manipulations of the interactions. Nano Lett. 16, 2322–2327 (2016).10.1021/acs.nanolett.5b05009 ↗
15. Park, S. et al. Direct determination of monolayer MoS2 and WSe2 exciton binding energies on insulating and metallic substrates. 2D Mater. 5, 025003 (2018).10.1088/2053-1583/aaa4ca ↗
16. Utama, M. I. B. et al. A dielectric-defined lateral heterojunction in a monolayer semiconductor. Nat. Electron. 2, 60–65 (2019).10.1038/s41928-019-0207-4 ↗
17. Li, H. et al. Growth of alloy MoS2xSe2(1−x) nanosheets with fully tunable chemical compositions and optical properties. J. Am. Chem. Soc. 136, 3756–3759 (2014).10.1021/ja500069b ↗
18. Conley, H. J. et al. Bandgap engineering of strained monolayer and bilayer MoS2. Nano Lett. 13, 3626–3630 (2013).10.1021/nl4014748 ↗
19. Chernikov, A. et al. Electrical tuning of exciton binding energies in monolayer WS2. Phys. Rev. Lett. 115, 126802 (2015).10.1103/PhysRevLett.115.126802 ↗
20. Waldecker, L. et al. Rigid band shifts in two-dimensional semiconductors through external dielectric screening. Phys. Rev. Lett. 123, 206403 (2019).10.1103/PhysRevLett.123.206403 ↗
21. Park, S. et al. The Schottky-Mott rule expanded for two-dimensional semiconductors: influence of substrate dielectric screening. ACS Nano 15, 14794–14803 (2021).10.1021/acsnano.1c04825 ↗
22. Britnell, L. et al. Electron tunneling through ultrathin boron nitride crystalline barriers. Nano Lett. 12, 1707 (2012).10.1021/nl3002205 ↗
23. Xu, W. et al. Determining the optimized interlayer separation distance in vertical stacked 2D WS2:hBN:MoS2 heterostructures for exciton energy transfer. Small 14, 1703727 (2018).10.1002/smll.201703727 ↗
24. Noori, K., Cheng, N. L. Q., Xuan, F. & Quek, S. Y. Dielectric screening by 2D substrates. 2D Mater. 6, 035036 (2019).10.1088/2053-1583/ab1e06 ↗
25. Riis-Jensen, A. C., Lu, J. & Thygesen, K. S. Electrically controlled dielectric band gap engineering in a two-dimensional semiconductor. Phys. Rev. B 101, 121110 (2020).10.1103/PhysRevB.101.121110 ↗
26. Qiu, Z. et al. Giant gate-tunable bandgap renormalization and excitonic effects in a 2D semiconductor. Sci. Adv. 5, 234 (2019).10.1126/sciadv.aaw2347 ↗
27. Xu, Y. et al. Creation of moiré bands in a monolayer semiconductor by spatially periodic dielectric screening. Nat. Mater. 20, 645–649 (2021).10.1038/s41563-020-00888-y ↗
28. Banszerus, L. et al. Ultrahigh-mobility graphene devices from chemical vapor deposition on reusable copper. Sci. Adv. 1, 1500222 (2015).10.1126/sciadv.1500222 ↗
29. Pizzocchero, F. et al. The hot pick-up technique for batch assembly of van der Waals heterostructures. Nat. Commun. 7, 11894 (2016).10.1038/ncomms11894 ↗
30. Winther, K. T. & Thygesen, K. S. Band structure engineering in van der Waals heterostructures via dielectric screening: the GΔW method. 2D Mater. 4, 025059 (2017).10.1088/2053-1583/aa6531 ↗
31. Selig, M. et al. Excitonic linewidth and coherence lifetime in monolayer transition metal dichalcogenides. Nat. Commun. 7, 13279 (2016).10.1038/ncomms13279 ↗
32. Pease, R. S. Crystal structure of boron nitride. Nature 165, 722–723 (1950).10.1038/165722b0 ↗
33. Neaton, J. B., Hybertsen, M. S. & Louie, S. G. Renormalization of molecular electronic levels at metal-molecule interfaces. Phys. Rev. Lett. 97, 216405 (2006).10.1103/PhysRevLett.97.216405 ↗
34. Garcia-Lastra, J. M., Rostgaard, C., Rubio, A. & Thygesen, K. S. Polarization-induced renormalization of molecular levels at metallic and semiconducting surfaces. Phys. Rev. B 80, 245427 (2009).10.1103/PhysRevB.80.245427 ↗
35. Haigh, S. J. et al. Cross-sectional imaging of individual layers and buried interfaces of graphene-based heterostructures and superlattices. Nat. Mater. 11, 764–767 (2012).10.1038/nmat3386 ↗
36. Rooney, A. P. et al. Observing imperfection in atomic interfaces for van der Waals heterostructures. Nano Lett. 17, 5222–5228 (2017).10.1021/acs.nanolett.7b01248 ↗
37. Hwang, E. H. & Das Sarma, S. Dielectric function, screening, and plasmons in two-dimensional graphene. Phys. Rev. B 75, 205418 (2007).10.1103/PhysRevB.75.205418 ↗
38. Zhu, B., Chen, X. & Cui, X. Exciton binding energy of monolayer WS2. Sci. Rep. 5, 9218 (2015).10.1038/srep09218 ↗
39. Froehlicher, G., Lorchat, E. & Berciaud, S. Charge versus energy transfer in atomically thin graphene-transition metal dichalcogenide van der Waals heterostructures. Phys. Rev. X 8, 011007 (2018).
40. Pierret, A. et al. Dielectric permittivity, conductivity and breakdown field of hexagonal boron nitride. Mater. Res. Express 9, 065901 (2022).10.1088/2053-1591/ac4fe1 ↗
41. Steinhoff, A., Wehling, T. O. & Rösner, M. Frequency-dependent substrate screening of excitons in atomically thin transition metal dichalcogenide semiconductors. Phys. Rev. B 98, 045304 (2018).10.1103/PhysRevB.98.045304 ↗
42. Sun, Z. et al. Charged bosons made of fermions in bilayer structures with strong metallic screening. Nano Lett. 21, 7669–7675 (2021).10.1021/acs.nanolett.1c02422 ↗
43. Wang, Z. et al. Evidence of high-temperature exciton condensation in two-dimensional atomic double layers. Nature 574, 76–80 (2019).10.1038/s41586-019-1591-7 ↗
44. Ma, L. et al. Strongly correlated excitonic insulator in atomic double layers. Nature 598, 585–589 (2021).10.1038/s41586-021-03947-9 ↗
45. Kumar, P. et al. Light-matter coupling in large-area van der Waals superlattices. Nat. Nanotechnol. 17, 182–189 (2022).10.1038/s41565-021-01023-x ↗
46. Müller, M. R. et al. Visibility of two-dimensional layered materials on various substrates. J. Appl. Phys. 118, 145305 (2015).10.1063/1.4930574 ↗
47. Alonso-Álvarez, D. et al. Solcore: a multi-scale, Python-based library for modelling solar cells and semiconductor materials. J. Comput. Electron. 17, 1099–1123 (2018).10.1007/s10825-018-1171-3 ↗
48. Lee, S. Y., Jeong, T. Y., Jung, S. & Yee, K. J. Refractive index dispersion of hexagonal boron nitride in the visible and near-infrared. Phys. Status Solidi B Basic Res. 256, 1800417 (2019).10.1002/pssb.201800417 ↗
49. Weber, J. W., Calado, V. E. & Van De Sanden, M. C. M. Optical constants of graphene measured by spectroscopic ellipsometry. Appl. Phys. Lett. 97, 091904 (2010).10.1063/1.3475393 ↗
50. Green, M. A. & Keevers, M. J. Optical properties of intrinsic silicon at 300 K. Prog. Photovolt. Res. Appl. 3, 189–192 (1995).10.1002/pip.4670030303 ↗
51. Malitson, I. H. Interspecimen comparison of the refractive index of fused silica. J. Opt. Soc. Am. 55, 1205 (1965).10.1364/JOSA.55.001205 ↗
52. Rytova, N. S. Screened potential of a point charge in a thin film. Vestn. Mosk. Univ. Fiz. Astron. 3, 30 (1967).