Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Visualizing electrostatic gating effects in two-dimensional heterostructures

Nature volume 572, pages 220–223 (2019)Cite this article

Subjects

Abstract

The ability to directly monitor the states of electrons in modern field-effect devices—for example, imaging local changes in the electrical potential, Fermi level and band structure as a gate voltage is applied—could transform our understanding of the physics and function of a device. Here we show that micrometre-scale, angle-resolved photoemission spectroscopy1,2,3 (microARPES) applied to two-dimensional van der Waals heterostructures4 affords this ability. In two-terminal graphene devices, we observe a shift of the Fermi level across the Dirac point, with no detectable change in the dispersion, as a gate voltage is applied. In two-dimensional semiconductor devices, we see the conduction-band edge appear as electrons accumulate, thereby firmly establishing the energy and momentum of the edge. In the case of monolayer tungsten diselenide, we observe that the bandgap is renormalized downwards by several hundreds of millielectronvolts—approaching the exciton energy—as the electrostatic doping increases. Both optical spectroscopy and microARPES can be carried out on a single device, allowing definitive studies of the relationship between gate-controlled electronic and optical properties. The technique provides a powerful way to study not only fundamental semiconductor physics, but also intriguing phenomena such as topological transitions5 and many-body spectral reconstructions under electrical control.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Visualizing electrostatic gating of monolayer graphene.
Fig. 2: Layer-number-dependent CBE in WSe2.
Fig. 3: Electrostatic gating of monolayer WSe2.
Fig. 4: Renormalization of the bandgap and comparison with optical spectroscopy.

Similar content being viewed by others

Data availability

All data presented in this paper are available at http://wrap.warwick.ac.uk/116301. Additional data related to this paper may be requested from the authors.

References

  1. Dudin, P. et al. Angle-resolved photoemission spectroscopy and imaging with a submicrometre probe at the Spectromicroscopy-3.2L beamline of Elettra. J. Synchrotron Radiat. 17, 445–450 (2010).

    Article  CAS  Google Scholar 

  2. Rotenberg, E. & Bostwick, A. MicroARPES and nanoARPES at diffraction-limited light sources: opportunities and performance gains. J. Synchrotron Radiat. 21, 1048–1056 (2014).

    Article  CAS  Google Scholar 

  3. Iwasawa, H. et al. Buried double CuO chains in YBa2Cu4O8 uncovered by nano-ARPES. J. Phys. Condens. Matter 4, 9015–9022 (2019).

    Google Scholar 

  4. Novoselov, K. S., Mishchenko, A., Carvalho, A. & Castro Neto, A. H. 2D materials and van der Waals heterostructures. Science 353, aac9439 (2016).

    Article  CAS  Google Scholar 

  5. Tong, Q. et al. Topological mosaics in moiré superlattices of van der Waals heterobilayers. Nat. Phys. 13, 356–362 (2017).

    Article  CAS  Google Scholar 

  6. Bostwick, A., Ohta, T., Seyller, T., Horn, K. & Rotenberg, E. Quasiparticle dynamics in graphene. Nat. Phys. 3, 36–40 (2007).

    Article  CAS  Google Scholar 

  7. Riley, J. M. et al. Negative electronic compressibility and tunable spin splitting in WSe2. Nat. Nanotechnol. 10, 1043–1047 (2015).

    Article  ADS  CAS  Google Scholar 

  8. Zhang, Y. et al. Electronic structure, surface doping, and optical response in epitaxial WSe2 thin films. Nano Lett. 16, 2485–2491 (2016).

    Article  ADS  CAS  Google Scholar 

  9. Kim, J. et al. Observation of tunable band gap and anisotropic Dirac semimetal state in black phosphorus. Science 349, 723–726 (2015).

    Article  CAS  Google Scholar 

  10. Tang, S. et al. Quantum spin Hall state in monolayer 1T′-WTe2. Nat. Phys. 13, 683–687 (2017).

    Article  CAS  Google Scholar 

  11. Koch, R. J. et al. Nano focusing of soft X-rays by a new capillary mirror optic. Synchrotron Radiat. News 31, 50–52 (2018).

    Article  Google Scholar 

  12. Zhang, H. et al. Resolving deep quantum-well states in atomically thin 2H-MoTe2 flakes by nanospot angle-resolved photoemission spectroscopy. Nano Lett. 18, 4664–4668 (2018).

    Article  ADS  CAS  Google Scholar 

  13. Katoch, J. et al. Giant spin-splitting and gap renormalization driven by trions in single-layer WS2/h-BN heterostructures. Nat. Phys. 14, 355–359 (2018).

    Article  CAS  Google Scholar 

  14. Cucchi, I. et al. Microfocus laser-angle-resolved photoemission on encapsulated mono-, bi-, and few-layer 1T′-WTe2. Nano Lett. 19, 554–560 (2019).

    Article  ADS  CAS  Google Scholar 

  15. Wilson, N. R. et al. Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures. Sci. Adv. 3, e1601832 (2017).

    Article  ADS  Google Scholar 

  16. Jin, W. et al. Tuning the electronic structure of monolayer graphene/MoS2 van der Waals heterostructures via interlayer twist. Phys. Rev. B 92, 201409 (2015).

    Article  ADS  Google Scholar 

  17. Pierucci, D. et al. Band alignment and minigaps in monolayer MoS2-graphene van der Waals heterostructures. Nano Lett. 16, 4054–4061 (2016).

    Article  ADS  CAS  Google Scholar 

  18. Liu, Y. et al. Van der Waals heterostructures and devices. Nat. Rev. Mater. 1, 16042 (2016).

    Article  ADS  CAS  Google Scholar 

  19. Schaibley, J. R. et al. Valleytronics in 2D materials. Nat. Rev. Mater. 1, 16055 (2016).

    Article  ADS  CAS  Google Scholar 

  20. Yankowitz, M., McKenzie, D. & LeRoy, B. J. Local spectroscopic characterization of spin and layer polarization in WSe2. Phys. Rev. Lett. 115, 136803 (2015).

    Article  ADS  Google Scholar 

  21. 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).

    Article  ADS  CAS  Google Scholar 

  22. He, K. et al. Tightly bound excitons in monolayer WSe2. Phys. Rev. Lett. 113, 026803 (2014).

    Article  ADS  Google Scholar 

  23. Park, S. et al. Direct determination of monolayer MoS2 and WSe2 exciton binding energies on insulating and metallic substrates. 2D Mater. 5, 025003 (2018).

    Article  Google Scholar 

  24. Stier, A. V. et al. Magnetooptics of exciton Rydberg states in a monolayer semiconductor. Phys. Rev. Lett. 120, 057405 (2018).

    Article  ADS  CAS  Google Scholar 

  25. Zhao, W., Ribeiro, R. M. & Eda, G. Electronic structure and optical signatures of semiconducting transition metal dichalcogenide nanosheets. Acc. Chem. Res. 48, 91–99 (2015).

    Article  CAS  Google Scholar 

  26. Mayorov, A. S. et al. Micrometer-scale ballistic transport in encapsulated graphene at room temperature. Nano Lett. 11, 2396–2399 (2011).

    Article  ADS  CAS  Google Scholar 

  27. Liu, G., Xiao, D., Yao, Y., Xu, X. & Yao, W. Electronic structures and theoretical modelling of two-dimensional group-VIB transition metal dichalcogenides. Chem. Soc. Rev. 44, 2643–2663 (2015).

    Article  CAS  Google Scholar 

  28. Ugeda, M. M. et al. Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor. Nat. Mater. 13, 1091–1095 (2014).

    Article  ADS  CAS  Google Scholar 

  29. Gao, S., Liang, Y., Spataru, C. D. & Yang, L. Dynamical excitonic effects in doped two-dimensional semiconductors. Nano Lett. 16, 5568–5573 (2016).

    Article  ADS  CAS  Google Scholar 

  30. Raja, A. et al. Coulomb engineering of the bandgap and excitons in two-dimensional materials. Nat. Commun. 8, 15251 (2017).

    Article  ADS  Google Scholar 

  31. Gao, S. & Yang, L. Renormalization of the quasiparticle band gap in doped two-dimensional materials from many-body calculations. Phys. Rev. B 96, 155410 (2017).

    Article  ADS  Google Scholar 

  32. Cao, Y. et al. Magic-angle graphene superlattices: a new platform for unconventional superconductivity. Nature 556, 43–50 (2018).

    Article  ADS  CAS  Google Scholar 

  33. Wang, H., Fan, F., Zhu, S. & Wu, H. Doping enhanced ferromagnetism and induced half-metallicity in CrI3 monolayer. EPL 114, 47001 (2016).

    Article  ADS  Google Scholar 

  34. Zomer, P. J., Guimarães, M. H. D., Brant, J. C., Tombros, N. & Van Wees, B. J. Fast pick up technique for high quality heterostructures of bilayer graphene and hexagonal boron nitride. Appl. Phys. Lett. 105, 013101 (2014).

    Article  ADS  Google Scholar 

  35. Fang, T., Konar, A., Xing, H. & Jena, D. Carrier statistics and quantum capacitance of graphene sheets and ribbons. Appl. Phys. Lett. 91, 092109 (2007).

    Article  ADS  Google Scholar 

  36. Yu, G. L. et al. Interaction phenomena in graphene seen through quantum capacitance. Proc. Natl Acad. Sci. USA 110, 3282–3286 (2013).

    Article  ADS  CAS  Google Scholar 

  37. Dean, C. R. et al. Boron nitride substrates for high-quality graphene electronics. Nat. Nanotechnol. 5, 722–726 (2010).

    Article  ADS  CAS  Google Scholar 

  38. Kim, K. K. et al. Synthesis and characterization of hexagonal boron nitride film as a dielectric layer for graphene devices. ACS Nano 6, 8583–8590 (2012).

    Article  CAS  Google Scholar 

  39. Mucha-Kruczyński, M. et al. Characterization of graphene through anisotropy of constant-energy maps in angle-resolved photoemission. Phys. Rev. B 77, 195403 (2008).

    Article  ADS  Google Scholar 

  40. Kormányos, A. et al. k·p theory for two-dimensional transition metal dichalcogenide semiconductors. 2D Mater. 2, 022001 (2015).

    Article  Google Scholar 

  41. Giannozzi, P. et al. QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials. J. Phys. Condens. Matter 21, 395502 (2009).

    Article  Google Scholar 

  42. Hamann, D. R. Optimized norm-conserving Vanderbilt pseudopotentials. Phys. Rev. B 88, 085117 (2013).

    Article  ADS  Google Scholar 

  43. van Setten, M. J. et al. The PSEUDODOJO: training and grading a 85 element optimized norm-conserving pseudopotential table. Comput. Phys. Commun. 226, 39–54 (2018).

    Article  ADS  Google Scholar 

  44. Marini, A., Hogan, C., Grüning, M. & Varsano, D. yambo: an ab initio tool for excited state calculations. Comput. Phys. Commun. 180, 1392–1403 (2009).

    Article  ADS  CAS  Google Scholar 

  45. Godby, R. W. & Needs, R. J. Metal-insulator transition in Kohn-Sham theory and quasiparticle theory. Phys. Rev. Lett. 62, 1169–1172 (1989).

    Article  ADS  CAS  Google Scholar 

  46. Castro, A., Räsänen, E. & Rozzi, C. A. Exact Coulomb cutoff technique for supercell calculations in two dimensions. Phys. Rev. B 80, 033102 (2009).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

Our research into monitoring gated electronic structure changes is supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award DE-SC0019443. Initial development of the samples and technique was done under award DE-SC0002197 via D.H.C. and P.V.N. Optical spectroscopy and partial sample fabrication were supported by award DE-SC0018171 (via X. Xu and N.P.W.). P.V.N. and J.K. received partial support from NSF Materials Research Science and Engineering Centers (MRSEC) award 1719797. N.R.W. and N.D.M.H. were supported through UK Engineering and Physical Sciences Research Council (EPSRC) award EP/P01139X/1. N.C.T., N.Y. and A.J.G. were supported through EPSRC studentships (EP/M508184/1 and EP/R513374/1). X. Xia was supported by a University of Warwick studentship. N.D.M.H. and G.C.C. were supported by the Winton Programme for the Physics of Sustainability. G.C.C. was supported by the Cambridge Trust European Scholarship. Computing resources were provided by the Darwin Supercomputer of the University of Cambridge High Performance Computing Service, the Scientific Computing Research Technology Platform of the University of Warwick, and the UK national high-performance computing service, ARCHER, via the UKCP consortium (EP/P022561/1).

Author information

Authors and Affiliations

  1. Department of Physics, University of Washington, Seattle, WA, USA

    Paul V. Nguyen, Nathan P. Wilson, Joshua Kahn, Xiaodong Xu & David H. Cobden

  2. Department of Physics, University of Warwick, Coventry, UK

    Natalie C. Teutsch, Xue Xia, Abigail J. Graham, Nelson Yeung, Nicholas D. M. Hine & Neil R. Wilson

  3. Elettra-Sincrotrone Trieste SCpA, Basovizza, Italy

    Viktor Kandyba, Alessio Giampietri & Alexei Barinov

  4. Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge, UK

    Gabriel C. Constantinescu

  5. Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA

    Xiaodong Xu

Authors
  1. Paul V. Nguyen
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Natalie C. Teutsch
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Nathan P. Wilson
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Joshua Kahn
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Xue Xia
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Abigail J. Graham
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Viktor Kandyba
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Alessio Giampietri
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Alexei Barinov
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. Gabriel C. Constantinescu
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. Nelson Yeung
    View author publications

    You can also search for this author in PubMed Google Scholar

  12. Nicholas D. M. Hine
    View author publications

    You can also search for this author in PubMed Google Scholar

  13. Xiaodong Xu
    View author publications

    You can also search for this author in PubMed Google Scholar

  14. David H. Cobden
    View author publications

    You can also search for this author in PubMed Google Scholar

  15. Neil R. Wilson
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

N.R.W., X. Xu and D.H.C. conceived and supervised the project. P.V.N., J.K. and N.P.W. fabricated the samples. N.C.T., N.R.W., P.V.N., X. Xia, A.J.G., V.K., A.G. and A.B. collected µ-ARPES data. N.C.T., N.R.W. and P.V.N. analysed µ-ARPES data (with input from A.B.). N.P.W. acquired photoluminescence data. N.D.M.H., N.Y. and G.C.C. performed the band-structure calculations. D.H.C., N.R.W., P.V.N. and X. Xu wrote the paper with input from all authors.

Corresponding authors

Correspondence to Xiaodong Xu, David H. Cobden or Neil R. Wilson.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Fabrication of a gated heterostructure.

Diagram showing the process for fabricating WSe2 device 1, with associated micrographs. Scale bars are 15 µm unless otherwise noted. PC, polycarbonate; PDMS, polydimethylsiloxane.

Extended Data Fig. 2 Distortion-free, uniform band shifting in electrostatically gated graphene.

a–c, Constant energy slices through a graphene Dirac cone at the stated gated voltages and electron energies relative to the Dirac point (black dot). No substantial change is seen on varying VG, implying that the spectrum is not distorted by electrostatic/space charge effects. The width of each panel represents 4 Å−1. d, Bottom, slice of energy E versus in-plane momentum k|| along the zone boundary, through points K and K′ (shown at the top), in gated graphene at VG = +3.35 V. Scale bar, 0.5 Å−1. The spectrum is symmetric about point M, as illustrated by the consistent Dirac-point energy (dashed line) between K and K′. These measurements are from the same device as Fig. 3, from a region in which the graphene was on top of the 1L WSe2 (which produces the faint bands at binding energies of around 2 eV) but still electrostatically gated. This shows that the electric field from the gate does not distort the measured graphene spectrum in any direction in momentum space.

Extended Data Fig. 3 Extracted graphene Fermi velocity versus gate voltage.

We calculated the Dirac-point energy and Fermi velocity from E − k slices (some of which are shown in Fig. 1) near the graphene K point, by analysing the band dispersions. We extracted momentum-distribution curves (MDCs; that is, intensity as a function of momentum I(k) at constant energy), and found the positions of the branches on each side of the Dirac cone by fitting Gaussian peaks. After repeating this process for each MDC within |E − EF| < 1 eV, we fit a straight line of the same absolute slope to each side, yielding the Dirac point, ED, from where the lines cross and the Fermi velocity, vF, from their slope. In cases in which one side was much more intense than the other, we used only the more intense side to find vF. The extracted velocity is here plotted against gate voltage. Evidence has previously been reported36 of a reduction in vF of up to 20% near ED in graphene films at low doping levels (roughly 1 × 1012 cm−2). This corresponds to a subtle distortion of the bands at ED, which the spectrometer at Elettra does not as yet have the resolution to probe, and could not be detected by the above procedure which assumes purely linear dispersion. Note that the variations seen in this figure can be explained by systematic errors, taking into account experimental limitations such as the very weak emission from one branch and the sensitivity to the exact alignment of the momentum slice with the Dirac point.

Extended Data Fig. 4 Uniform band shifting in electrostatically gated 2L WSe2.

Constant energy maps of electrostatically gated 2L WSe2 at VG = +8 V: left, at a binding energy of 1.555 eV, which here corresponds to the valence-band maximum; and right, near the Fermi energy at a binding energy of 0.025 eV. It can be seen that the CBE is the same at points Q and Q′, implying that the gate field does not substantially distort the spectrum in this case either.

Extended Data Fig. 5 CBEs in monolayer MoS2, MoSe2 and WS2.

a, Diagram of a device, with graphene contact grounded and gate voltage applied to the graphite back gate, as in Fig. 2a. b, Diagram showing the bands near point K, at zero gate voltage (left) and at a gate voltage that exceeds the threshold voltage to bring the Fermi level to the CBE (right). CBM, conduction-band maximum; VBM, valence-band maximum. c–e, Energy-momentum slices through point for monolayer MoS2, MoSe2 and WS2. Scale bars, 0.3 Å−1.

Extended Data Fig. 6 Photocurrent and SPEM maps of a WSe2 heterostructure device.

a, Diagram of the device, with the graphene contact grounded and a gate voltage applied to the graphite back gate. b, c, Optical (b) and SPEM (c) images of WSe2 device 1, with 1L, 2L and 3L regions identified. Dashed lines trace boundaries of the graphite gate (red) and the graphene contact (black). d, Photocurrent image acquired simultaneously with the SPEM image in panel c. Scale bars, 5 µm.

Extended Data Fig. 7 Gate-induced band shifts and photocurrent in monolayer WSe2.

a, ΔEΓ versus VG for WSe2 monolayer device 2. b, VG − ΔEΓ/e versus VG. c, Current from gate to ground versus VG. The grey shaded regions indicate the threshold regions in which the WSe2 becomes conducting. See Methods for discussion.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Nguyen, P.V., Teutsch, N.C., Wilson, N.P. et al. Visualizing electrostatic gating effects in two-dimensional heterostructures. Nature 572, 220–223 (2019). https://doi.org/10.1038/s41586-019-1402-1

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41586-019-1402-1

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing