Probing excitonic states in suspended two-dimensional semiconductors by photocurrent spectroscopy

Abstract

The optical response of semiconducting monolayer transition-metal dichalcogenides (TMDCs) is dominated by strongly bound excitons that are stable even at room temperature. However, substrate-related effects such as screening and disorder in currently available specimens mask many anticipated physical phenomena and limit device applications of TMDCs. Here, we demonstrate that that these undesirable effects are strongly suppressed in suspended devices. Extremely robust (photogain > 1,000) and fast (response time < 1 ms) photoresponse allow us to study, for the first time, the formation, binding energies and dissociation mechanisms of excitons in TMDCs through photocurrent spectroscopy. By analyzing the spectral positions of peaks in the photocurrent and by comparing them with first-principles calculations, we obtain binding energies, band gaps and spin-orbit splitting in monolayer TMDCs. For monolayer MoS 2 , in particular, we obtain an extremely large binding energy for band-edge excitons, E bind ≥ 570 meV. Along with band-edge excitons, we observe excitons associated with a van Hove singularity of rather unique nature. The analysis of the source-drain voltage dependence of photocurrent spectra reveals exciton dissociation and photoconversion mechanisms in TMDCs.

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References 63

1. 1.

   Wang Q. H., Kalantar-Zadeh K., Kis A., Coleman J. N. & Strano M. S. Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. Nat Nanotechnol 7, 699–712 (2012 ).

   Not in our library10.1038/nnano.2012.193

2. 2.

   Novoselov K. S. et al. Two-dimensional atomic crystals. Proc Nat Acad Sci USA 102, 10451–10453 (2005 ).

   Not in our library10.1073/pnas.0502848102

3. 3.

   Radisavljevic B., Radenovic A., Brivio J., Giacometti V. & Kis A. Single-layer MoS2 transistors. Nat Nanotechnol 6, 147–150 (2011 ).

   Not in our library10.1038/nnano.2010.279

4. 4.

   Castro Neto A. H., Guinea F., Peres N. M. R., Novoselov K. S. & Geim A. K. The electronic properties of graphene. Rev Mod Phys 81, 109–162 (2009 ).

   Not in our library

5. 5.

   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 ).

   Not in our library10.1103/physrevlett.105.136805

6. 6.

   Xiao D., Liu G. B., Feng W. X., Xu X. D. & Yao W. Coupled Spin and Valley Physics in Monolayers of MoS2 and Other Group-VI Dichalcogenides. Phys Rev Lett 108, 196802 (2012 ).

   Not in our library10.1103/physrevlett.108.196802

7. 7.

   Splendiani A. et al. Emerging Photoluminescence in Monolayer MoS2. Nano Lett 10, 1271–1275 (2010 ).

   Not in our library10.1021/nl903868w

8. 8.

   Zeng H. L., Dai J. F., Yao W., Xiao D. & Cui X. D. Valley polarization in MoS2 monolayers by optical pumping. Nat Nanotechnol 7, 490–493 (2012 ).

   Not in our library10.1038/nnano.2012.95

9. 9.

   Mak K. F., He K. L., Shan J. & Heinz T. F. Control of valley polarization in monolayer MoS2 by optical helicity. Nat Nanotechnol 7, 494–498 (2012 ).

   Not in our library10.1038/nnano.2012.96

10. 10.

    Sallen G. et al. Robust optical emission polarization in MoS2 monolayers through selective valley excitation. Phys Rev B 86, 081301 (2012 ).

    Not in our library

11. 11.

    Cao T. et al. Valley-selective circular dichroism of monolayer molybdenum disulphide. Nat Commun 3, 887 (2012 ).

    Not in our library10.1038/ncomms1882

12. 12.

    Mak K. F. et al. Tightly bound trions in monolayer MoS2. Nat Mater 12, 207–211 (2013 ).

    Not in our library10.1038/nmat3505

13. 13.

    Ross J. S. et al. Electrical control of neutral and charged excitons in a monolayer semiconductor. Nat Commun 4, 1474 (2013 ).

    Not in our library10.1038/ncomms2498

14. 14.

    Newaz A. K. M. et al. Electrical control of optical properties of monolayer MoS2. Solid State Commun 155, 49–52 (2013 ).

    Not in our library

15. 15.

    Li X., Zhang F. & Niu Q. Unconventional Quantum Hall Effect and Tunable Spin Hall Effect in Dirac Materials: Application to an Isolated MoS2 Trilayer. Phys Rev Lett 110, 066803 (2013 ).

    Not in our library10.1103/physrevlett.110.066803

16. 16.

    Mak K. F., McGill K. L., Park J. & McEuen P. L. The valley Hall effect in MoS2 transistors. Science 344, 1489–1492 (2014 ).

    Not in our library10.1126/science.1250140

17. 17.

    Roldán R., Cappelluti E. & Guinea F. Interactions and superconductivity in heavily doped MoS2. Phys Rev B 88, 054515 (2013 ).

    Not in our library

18. 18.

    Geim A. K. & Grigorieva I. V. Van der Waals heterostructures. Nature 499, 419–425 (2013 ).

    Not in our library10.1038/nature12385

19. 19.

    Wigner E. On the Interaction of Electrons in Metals. Phys Rev 46, 1002–1011 (1934 ).

    Not in our library

20. 20.

    Britnell L. et al. Strong Light-Matter Interactions in Heterostructures of Atomically Thin Films. Science 340, 1311–1314 (2013 ).

    Not in our library10.1126/science.1235547

21. 21.

    Lopez-Sanchez O., Lembke D., Kayci M., Radenovic A. & Kis A. Ultrasensitive photodetectors based on monolayer MoS2. Nat Nanotechnol 8, 497–501 (2013 ).

    Not in our library10.1038/nnano.2013.100

22. 22.

    Tsai D.-S. et al. Few-Layer MoS2 with High Broadband Photogain and Fast Optical Switching for Use in Harsh Environments. ACS Nano 7, 3905–3911 (2013 ).

    Not in our library10.1021/nn305301b

23. 23.

    Wu C.-C. et al. Elucidating the Photoresponse of Ultrathin MoS2 Field-Effect Transistors by Scanning Photocurrent Microscopy. J Phys Chem Lett 4, 2508–2513 (2013 ).

    Not in our library

24. 24.

    Yin Z. et al. Single-Layer MoS2 Phototransistors. ACS Nano 6, 74–80 (2011 ).

    Not in our library10.1021/nn2024557

25. 25.

    Bernardi M., Palummo M. & Grossman J. C. Extraordinary Sunlight Absorption and One Nanometer Thick Photovoltaics Using Two-Dimensional Monolayer Materials. Nano Lett 13, 3664–3670 (2013 ).

    Not in our library10.1021/nl401544y

26. 26.

    Qiu D. Y., da Jornada F. H. & Louie S. G. Optical Spectrum of MoS2: Many-Body Effects and Diversity of Exciton States. Phys Rev Lett 111, 216805 (2013 ).

    Not in our library10.1103/physrevlett.111.216805

27. 27.

    Ramasubramaniam A. Large excitonic effects in monolayers of molybdenum and tungsten dichalcogenides. Phys Rev B 86, 115409 (2012 ).

    Not in our library

28. 28.

    Bolotin K. I. et al. Ultrahigh electron mobility in suspended graphene. Solid State Commun 146, 351–355 (2008 ).

    Not in our library

29. 29.

    Jin T., Kang J., Su Kim E., Lee S. & Lee C. Suspended single-layer MoS2 devices. J Appl Phys 114, 164509 (2013 ).

    Not in our library

30. 30.

    Berkelbach T. C., Hybertsen M. S. & Reichman D. R. Theory of neutral and charged excitons in monolayer transition metal dichalcogenides. Phys Rev B 88, 045318 (2013 ).

    Not in our library

31. 31.

    Baugher B. W. H., Churchill H. O. H., Yang Y. & Jarillo-Herrero P. Intrinsic Electronic Transport Properties of High-Quality Monolayer and Bilayer MoS2. Nano Lett 13, 4212–4216 (2013 ).

    Not in our library10.1021/nl401916s

32. 32.

    Bao W. Z., Cai X. H., Kim D., Sridhara K. & Fuhrer M. S. High mobility ambipolar MoS2 field-effect transistors: Substrate and dielectric effects. Appl Phys Lett 102, 042104 (2013 ).

    Not in our library

33. 33.

    Radisavljevic B. & Kis A. Mobility engineering and a metal–insulator transition in monolayer MoS2. Nat Mater 12, 815–820 (2013 ).

    Not in our library10.1038/nmat3687

34. 34.

    Eda G. et al. Photoluminescence from Chemically Exfoliated MoS2. Nano Lett 12, 526–526 (2012 ).

    Not in our library10.1021/nl201874w

35. 35.

    Soci C. et al. Nanowire Photodetectors. J Nanosci Nanotechno 10, 1430–1449 (2010 ).

    Not in our library10.1166/jnn.2010.2157

36. 36.

    Collins R. T., Klitzing K. v. & Ploog K. Photocurrent spectroscopy of GaAs/AlxGa1−xAs quantum wells in an electric field. Phys Rev B 33, 4378–4381 (1986 ).

    Not in our library10.1103/physrevb.33.4378

37. 37.

    Mar J. D. et al. High-resolution photocurrent spectroscopy of the positive trion state in a single quantum dot. Phys Rev B 87, 155315 (2013 ).

    Not in our library

38. 38.

    Buscema M. et al. Large and Tunable Photothermoelectric Effect in Single-Layer MoS2. Nano Lett 13, 358–363 (2013 ).

    Not in our library10.1021/nl303321g

39. 39.

    Chemla D. S. & Shah J. Many-body and correlation effects in semiconductors. Nature 411, 549–557 (2001 ).

    Not in our library10.1038/35079000

40. 40.

    Kam K. K. & Parkinson B. A. Detailed Photocurrent Spectroscopy of the Semiconducting Group-Vi Transition-Metal Dichalcogenides. J Phys Chem 86, 463–467 (1982 ).

    Not in our library

41. 41.

    Nagpal P. & Klimov V. I. Role of mid-gap states in charge transport and photoconductivity in semiconductor nanocrystal films. Nat Commun 2, 486–493 (2011 ).

    Not in our library10.1038/ncomms1492

42. 42.

    Freitag M., Low T., Xia F. N. & Avouris P. Photoconductivity of biased graphene. Nat Photonics 7, 53–59 (2013 ).

    Not in our library

43. 43.

    Konstantatos G. et al. Hybrid graphene-quantum dot phototransistors with ultrahigh gain. Nat Nanotechnol 7, 363–368 (2012 ).

    Not in our library10.1038/nnano.2012.60

44. 44.

    Molina-Sánchez A., Sangalli D., Hummer K., Marini A. & Wirtz L. Effect of spin-orbit interaction on the optical spectra of single-layer, double-layer, and bulk MoS2. Phys Rev B 88, 045412 (2013 ).

    Not in our library

45. 45.

    Rohlfing M. & Louie S. G. Electron-hole excitations and optical spectra from first principles. Phys Rev B 62, 4927–4944 (2000 ).

    Not in our library

46. 46.

    Hüser F., Olsen T. & Thygesen K. S. How dielectric screening in two-dimensional crystals affects the convergence of excited-state calculations: Monolayer MoS2. Phys Rev B 88, 245309 (2013 ).

    Not in our library

47. 47.

    Skinner B., Shklovskii B. I. & Voloshin M. B. Bound state energy of a Coulomb impurity in gapped bilayer graphene. Phys Rev B 89, 041405 (2014 ).

    Not in our library

48. 48.

    Dolui K., Rungger I. & Sanvito S. Origin of the n-type and p-type conductivity of MoS2 monolayers on a SiO2 substrate. Phys Rev B 87, 165402 (2013 ).

    Not in our library

49. 49.
    Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged and free excitons · 2013

    No notice
50. 50.

    Yang X. L., Guo S. H., Chan F. T., Wong K. W. & Ching W. Y. Analytic solution of a two-dimensional hydrogen atom. I. Nonrelativistic theory. Phys Rev A 43, 1186–1196 (1991 ).

    Not in our library10.1103/physreva.43.1186

51. 51.

    Komsa H.-P. & Krasheninnikov A. V. Effects of confinement and environment on the electronic structure and exciton binding energy of MoS2 from first principles. Phys Rev B 86, 241201 (2012 ).

    Not in our library

52. 52.

    Ribeiro L. A. et al. Exciton dissociation and charge carrier recombination processes in organic semiconductors. J Chem Phys 135, 224901 (2011 ).

    Not in our library10.1063/1.3665392

53. 53.

    Mohite A. D., Gopinath P., Shah H. M. & Alphenaar B. W. Exciton dissociation and stark effect in the carbon nanotube photocurrent spectrum. Nano Lett 8, 142–146 (2008 ).

    Not in our library10.1021/nl0722525

54. 54.

    Gregg B. A. Excitonic solar cells. J Phys Chem B 107, 4688–4698 (2003 ).

    Not in our library

55. 55.

    Ng K. K. Complete guide to semiconductor devices. International edn, 439–444 (McGraw-Hill, New York, 2002 ).

    Not in our library

56. 56.

    Fontana M. et al. Electron-hole transport and photovoltaic effect in gated MoS2 Schottky junctions. Sci. Rep. 3, 1634 (2013 ).

    Not in our library10.1038/srep01634

57. 57.

    Liu H. C. et al. Multicolor voltage-tunable quantum-well infrared photodetector. Electron Device Letters, IEEE 14, 566–568 (1993 ).

    Not in our library

58. 58.

    Eda G. & Maier S. A. Two-Dimensional Crystals: Managing Light for Optoelectronics. ACS Nano 7, 5660–5665 (2013 ).

    Not in our library10.1021/nn403159y

59. 59.
    Exciton Binding Energy of Monolayer WS2 · 2015

    No notice
60. 60.

    Ye Z. et al. Probing Excitonic Dark States in Single-layer Tungsten Disulfide. arXiv:1403.5568 (2014 ).

    Not in our library10.1038/nature13734

61. 61.

    Wang G. et al. Non-linear Optical Spectroscopy of Excited Exciton States for Efficient Valley Coherence Generation in WSe2 Monolayers. arXiv:1404.0056 (2014 ).

    Not in our library

62. 62.

    Chernikov A. et al. Non-Hydrogenic Exciton Rydberg Series in Monolayer WS2. arXiv:1403.4270 (2014 ).

    Not in our library

63. 63.

    He K. et al. Tightly Bound Excitons in Monolayer WSe2. Phys Rev Lett 113, 026803 (2014 ).

    Not in our library10.1103/physrevlett.113.026803

Cited by papers we hold 3

• Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures · 2017
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• Trion fine structure and coupled spin–valley dynamics in monolayer tungsten disulfide · 2016
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• Exciton–polaritons in van der Waals heterostructures embedded in tunable microcavities · 2015
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