Momentum-forbidden dark excitons in hBN-encapsulated monolayer MoS2
Source abstract
Abstract
Abstract Encapsulation by hexagonal boron nitride (hBN) has been widely used to address intrinsic properties of two-dimensional (2D) materials. The hBN encapsulation, however, can alter properties of 2D materials through interlayer orbital hybridization. In this paper, we present measurements of temperature dependence of photoluminescence intensity from monolayer MoS2 encapsulated by hBN flakes. The obtained temperature dependence shows an opposite trend to that of previously observed in a monolayer MoS2 on a SiO2 substrate. This is caused by the existence of stable momentum-forbidden dark excitons in the hBN-encapsulated MoS2. Ab-initio band-structure calculations have shown that orbital hybridization between MoS2 and hBN leads to upward shift of Γ-valley of MoS2, which results in lowering of energy of the momentum-forbidden dark excitons. This work shows an important implication that the hBN-encapsulated structures used to address intrinsic properties of two-dimensional crystals can alter basic properties of encapsulated materials.
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Research context
OpenAlex topics: 2D Materials and Applications · Graphene research and applications · MXene and MAX Phase Materials
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References (33)
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1. Kitaura, R. et al. Chemical vapor deposition growth of graphene and related materials. J. Phys. Soc. Jpn 84, 121013-1-13 (2015).10.7566/JPSJ.84.121013 ↗
2. Mak, K. F., Lee, C., Hone, J., Shan, J. & Heinz, T. F. Atomically thin MoS2: a new direct-gap semiconductor. Phys. Rev. Lett. 105, 136805-1-4 (2010).10.1103/PhysRevLett.105.136805 ↗
3. Novoselov, K. S. et al. Two-dimensional gas of massless Dirac fermions in graphene. Nature 438, 197–200 (2005).10.1038/nature04233 ↗
4. Li, L. K. et al. Black phosphorus field-effect transistors. Nat. Nanotechnol. 9, 372–377 (2014).10.1038/nnano.2014.35 ↗
5. 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).10.1038/nnano.2012.193 ↗
6. Duong, D. L., Yun, S. J. & Lee, Y. H. van der Waals layered materials: opportunities and challenges. ACS Nano 11, 11803–11830 (2017).10.1021/acsnano.7b07436 ↗
7. Wang, G. et al. Colloquium: excitons in atomically thin transition metal dichalcogenides. Rev. Mod. Phys. 90, 021001-1-25 (2018).10.1103/RevModPhys.90.021001 ↗
8. Choi, W. et al. Recent development of two-dimensional transition metal dichalcogenides and their applications. Mater. Today 20, 116–130 (2017).10.1016/j.mattod.2016.10.002 ↗
9. 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, 196802-1-5 (2012).10.1103/PhysRevLett.108.196802 ↗
10. Rivera, P. et al. Interlayer valley excitons in heterobilayers of transition metal dichalcogenides. Nat. Nanotechnol. 13, 1004–1015 (2018).10.1038/s41565-018-0193-0 ↗
11. Tsen, A. W. et al. Nature of the quantum metal in a two-dimensional crystalline superconductor. Nat. Phys. 12, 208–212 (2016).10.1038/nphys3579 ↗
12. Cui, X. et al. Multi-terminal transport measurements of MoS2 using a van der Waals heterostructure device platform. Nat. Nanotechnol. 10, 534–540 (2015).10.1038/nnano.2015.70 ↗
13. Wu, S. F. et al. Observation of the quantum spin Hall effect up to 100 kelvin in a monolayer crystal. Science 359, 76–79 (2018).10.1126/science.aan6003 ↗
14. Ma, Q. et al. Observation of the nonlinear Hall effect under time-reversal-symmetric conditions. Nature 565, 337–346 (2019).10.1038/s41586-018-0807-6 ↗
15. Dean, C. R. et al. Boron nitride substrates for high-quality graphene electronics. Nat. Nanotechnol. 5, 722–726 (2010).10.1038/nnano.2010.172 ↗
16. Lee, G. H. et al. Highly stable, dual-gated MoS2 transistors encapsulated by hexagonal boron nitride with gate-controllable contact, resistance, and threshold voltage. ACS Nano 9, 7019–7026 (2015).10.1021/acsnano.5b01341 ↗
17. Yu, H. et al. Precisely aligned monolayer MoS2 epitaxially grown on h-BN basal plane. Small 13, 1603005 (2017).10.1002/smll.201603005 ↗
18. Gutierrez, H. R. et al. Extraordinary room-temperature photoluminescence in triangular WS2 monolayers. Nano Lett. 13, 3447–3454 (2013).10.1021/nl3026357 ↗
19. Okada, M. et al. Direct chemical vapor deposition growth of WS2 atomic layers on hexagonal boron nitride. ACS Nano 8, 8273–8277 (2014).10.1021/nn503093k ↗
20. Zhao, W. J. et al. Evolution of electronic structure in atomically thin sheets of WS2 and WSe2. ACS Nano 7, 791–797 (2013).10.1021/nn305275h ↗
21. Cao, Y. et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature 556, 43–50 (2018).10.1038/nature26160 ↗
22. Cao, Y. et al. Correlated insulator behaviour at half-filling in magic-angle graphene superlattices. Nature 556, 80–84 (2018).10.1038/nature26154 ↗
23. Rosenberger, M. R. et al. Nano-“squeegee” for the creation of clean 2D material interfaces. ACS Appl. Mater. Interfaces. 10, 10379–10387 (2018).10.1021/acsami.8b01224 ↗
24. Kaplan, D. et al. Excitation intensity dependence of photoluminescence from monolayers of MoS2 and WS2/MoS2 heterostructures. 2D Materials 3, 015005–1 (2016).10.1088/2053-1583/3/1/015005 ↗
25. Zafar, A. et al. Probing the intrinsic optical quality of CVD grown MoS2. Nano Res. 10, 1608–1617 (2017).10.1007/s12274-016-1319-z ↗
26. Okada, M. et al. Observation of biexcitonic emission at extremely low power density in tungsten disulfide atomic layers grown on hexagonal boron nitride. Sci. Rep. 7, 322-1-7 (2017).10.1038/s41598-017-00068-0 ↗
27. Okada, M. et al. Direct and indirect interlayer excitons in a van der Waals heterostructure of hBN/WS2/MoS2/hBN. ACS Nano 12, 2498–2505 (2018).10.1021/acsnano.7b08253 ↗
28. Zhang, X. X., You, Y. M., Zhao, S. Y. F. & Heinz, T. F. Experimental evidence for dark excitons in monolayer WSe2. Phys. Rev. Lett. 115, 257403-1-6 (2015).10.1103/PhysRevLett.115.257403 ↗
29. Malic, E. et al. Dark excitons in transition metal dichalcogenides. Phys. Rev. Mater. 2, 014002-1-7 (2018).10.1103/PhysRevMaterials.2.014002 ↗
30. Peelaers, H. & Van de Walle, C. G. Effects of strain on band structure and effective masses in MoS2. Phys. Rev. B 86, 241401-1-5 (2012).10.1103/PhysRevB.86.241401 ↗
31. Giannozzi, P. et al. QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials. J. Phys. Condens. Mater. 21, 395502-1-19 (2009).
32. Blochl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).10.1103/PhysRevB.50.17953 ↗
33. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 78, 3865–3868 (1997).10.1103/PhysRevLett.77.3865 ↗