The science and applications of electronics and optoelectronics have been driven for decades by progress in the growth of semiconducting heterostructures. Many applications in the infrared and terahertz frequency range exploit transitions between quantized states in semiconductor quantum wells (intersubband transitions). However, current quantum well devices are limited in functionality and versatility by diffusive interfaces and the requirement of lattice-matched growth conditions. Here, we introduce the concept of intersubband transitions in van der Waals quantum wells and report their first experimental observation. Van der Waals quantum wells are naturally formed by two-dimensional materials and hold unexplored potential to overcome the aforementioned limitations—they form atomically sharp interfaces and can easily be combined into heterostructures without lattice-matching restrictions. We employ near-field local probing to spectrally resolve intersubband transitions with a nanometre-scale spatial resolution and electrostatically control the absorption. This work enables the exploitation of intersubband transitions with unmatched design freedom and individual electronic and optical control suitable for photodetectors, light-emitting diodes and lasers.
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Kroemer, H. Nobel lecture: Quasi-electric fields and band offset: teaching electrons new tricks. Rev. Mod. Phys. 73, 783–793 (2001).
Alferov, Z. I. Nobel lecture: The double heterostructure concept and its applications in physics, electronics, and technology. Rev. Mod. Phys. 73, 767–782 (2001).
Hayashi, I., Panish, M. B., Foy, P. W. & Sumski, S. Junction lasers which operate continuously at room temperature. Appl. Phys. Lett. 17, 109–111 (1970).
Nakamura, S., Mukai, T. & Senoh, M. Candela-class high-brightness InGaN/AlGaN double-heterostructure blue-light-emitting diodes. Appl. Phys. Lett. 64, 1687–1689 (1994).
Bhattacharya, P. & Mi, Z. Quantum-dot optoelectronic devices. Proc. IEEE 95, 1723–1740 (2007).
Wang, J., Gudiksen, M. S., Duan, X., Cui, Y. & Lieber, C. M. Highly polarized photoluminescence and photodetection from single indium phosphide nanowires. Science 293, 1455–1457 (2001).
Levine, B. F. Quantum well infrared photodetectors. J. Appl. Phys. 74, R1–R81 (1993).
Faist, J. et al. Quantum cascade laser. Science 264, 553–556 (1994).
West, L. C. & Eglash, S. J. First observation of an extremely large-dipole infrared transition within the conduction band of a GaAs quantum well. Appl. Phys. Lett. 46, 1156–1158 (1985).
Helm, M. Intersubband semiconductor light sources: history, status, and future. In Infrared and Millimeter Waves, Conference Digest of the 2004 Joint 29th International Conference on 2004 and 12th International Conference on Terahertz Electronics (IEEE, 2004).
Liu, H. C., & Capasso, F. Intersubband Transitions in Quantum Wells: Physics and Device Applications (Elsevier, Amsterdam, 1999).
Warwick, C. A., Jan, W. Y., Ourmazd, A. & Harris, T. D. Does luminescence show semiconductor interfaces to be atomically smooth? Appl. Phys. Lett. 56, 2666–2668 (1990).
Novoselov, K. S. et al. Two-dimensional atomic crystals. Proc. Natl Acad. Sci. USA 102, 10451–10453 (2005).
Novoselov, K. S., Mishchenko, A., Carvalho, A. & Castro Neto, A. H. 2D materials and van der Waals heterostructures. Science 353, 461 (2016).
Mak, K. F. & Shan, J. Photonics and optoelectronics of 2D semiconductor transition metal dichalcogenides. Nat. Photon. 10, 216–226 (2016).
Wang, Q. H., Kalantar-Zadeh, K., Kis, A., Coleman, J. N. & Strano, M. S. Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. Nat. Nanotech. 7, 699–712 (2012).
Koppens, F. H. L. et al. Photodetectors based on graphene, other two-dimensional materials and hybrid systems. Nat. Nanotech. 9, 780–793 (2014).
Cui, X. et al. Multi-terminal transport measurements of MoS2 using a van der Waals heterostructure device platform. Nat. Nanotech. 10, 534–540 (2015).
Xu, S. et al. Odd-integer quantum Hall states and giant spin susceptibility in p-type few-layer WSe2. Phys. Rev. Lett. 118, 067702 (2017).
Bandurin, D. A. et al. High electron mobility, quantum Hall effect and anomalous optical response in atomically thin InSe. Nat. Nanotech. 12, 223–227 (2017).
Schaibley, J. R. et al. Valleytronics in 2D materials. Nat. Rev. Mater. 1, 1–15 (2016).
Mak, K. F., McGill, K. L., Park, J. & McEuen, P. L. The valley Hall effect in MoS2 transistors. Science 344, 1489–92 (2014).
Back, P., Zeytinoglu, S., Ijaz, A., Kroner, M. & Imamoǧlu, A. Realization of an electrically tunable narrow-bandwidth atomically thin mirror using monolayer MoSe2. Phys. Rev. Lett. 120, 037401 (2018).
Scuri, G. et al. Large excitonic reflectivity of monolayer MoSe2 encapsulated in Hexagonal Boron Nitride. Phys. Rev. Lett. 120, 037402 (2018).
Cadiz, F. et al. Excitonic linewidth approaching the homogeneous limit in MoS2-based van der Waals heterostructures. Phys. Rev. X 7, 021026 (2017).
Ajayi, O. A. et al. Approaching the intrinsic photoluminescence linewidth in transition metal dichalcogenide monolayers. 2D Mater. 4, 031011 (2017).
Wang, L. et al. One-dimensional electrical contact to a two-dimensional material. Science 342, 614–7 (2013).
Britnell, L. et al. Field-effect tunneling transistor based on vertical graphene heterostructures. Science 335, 947–950 (2012).
Keilmann, F. & Hillenbrand, R. Near-field microscopy by elastic light scattering from a tip. Phil. Trans. R. Soc. A 362, 787–805 (2004).
Ruiz-Tijerina, D. A., Danovich, M., Yelgel, C., Zólyomi, V. & Fal’ko, V. Hybrid k·p tight-binding model for subbands and infrared intersubband optics in few-layer films of transition metal dichalcogenides: MoS2, MoSe2, WS2, and WSe2. Phys. Rev. B 98, 035411 (2018).
Kormányos, A. et al. k·p theory for two-dimensional transition metal dichalcogenide semiconductors. 2D Mater. 2, 22001 (2014).
Sahin, H. et al. Anomalous Raman spectra and thickness-dependent electronic properties of WSe2. Phys. Rev. B 87, 165409 (2013).
Huang, W., Luo, X., Gan, C. K., Quek, S. Y. & Liang, G. Theoretical study of thermoelectric properties of few-layer MoS2 and WSe2. Phys. Chem. Chem. Phys. 16, 10866 (2014).
Kane, M. J., Emeny, M. T., Apsley, N., Whitehouse, C. R. & Lee, D. Inter-sub-band absorption in GaAs/AlGaAs single quantum wells. Semicond. Sci. Technol. 3, 722–725 (1988).
Huth, F. et al. Nano-FTIR absorption spectroscopy of molecular fingerprints at 20 nm spatial resolution. Nano Lett. 12, 3973–3978 (2012).
Taubner, T., Hillenbrand, R. & Keilmann, F. Nanoscale polymer recognition by spectral signature in scattering infrared near-field microscopy. Appl. Phys. Lett. 85, 5064–5066 (2004).
Govyadinov, A. A., Amenabar, I., Huth, F., Carney, P. S. & Hillenbrand, R. Quantitative measurement of local infrared absorption and dielectric function with tip-enhanced near-field microscopy. J. Phys. Chem. Lett. 4, 1526–1531 (2013).
Govyadinov, A. A. et al. Recovery of permittivity and depth from near-field data as a step toward infrared nanotomography. ACS Nano 8, 6911–6921 (2014).
Manasreh, M. O. et al. Origin of the blueshift in the intersubband infrared absorption in GaAs/Al0.3Ga0.7As multiple quantum well. Phys. Rev. B 43, 9996–9999 (1991).
Allen, S. J., Tsui, D. C. & Vinter, B. On the absorption of infrared radiation by electrons in semiconductor inversion layers. Solid State Commun. 88, 425–428 (1993).
Unuma, T., Yoshita, M., Noda, T., Sakaki, H. & Akiyama, H. Intersubband absorption linewidth in GaAs quantum wells due to scattering by interface roughness, phonons, alloy disorder, and impurities. J. Appl. Phys. 93, 1586–1597 (2003).
Tsujino, S. et al. Interface-roughness-induced broadening of intersubband electroluminescence in p-SiGe and n-GaInAs/AlInAs quantum-cascade structures. Appl. Phys. Lett. 86, 062113 (2005).
Fei, Z. et al. Infrared nanoscopy of Dirac plasmons at the graphene–SiO2 interface. Nano Lett. 11, 4701–4705 (2011).
Kurman, Y. et al. Control of semiconductor emitter frequency by increasing polariton momenta. Nat. Photon. 12, 423–429 (2018).
Edelberg, D. et al. Hundredfold enhancement of light emission via defect control in monolayer transition-metal dichalcogenides. Preprint at https://arxiv.org/abs/1805.00127 (2018).
Geim, A. K. & Grigorieva, I. V. Van der Waals heterostructures. Nature 499, 419–25 (2013).
Fei, Z. et al. Edge conduction in monolayer WTe2. Nat. Phys. 13, 677–682 (2017).
Wu, S. et al. Observation of the quantum spin Hall effect up to 100 Kelvin in a monolayer crystal. Science 359, 76–79 (2018).
Xi, X. et al. Ising pairing in superconducting NbSe2 atomic layers. Nat. Phys. 12, 139–143 (2015).
Huang, B. et al. Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit. Nature 546, 270–273 (2017).
Gong, C. et al. Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals. Nature 546, 265–269 (2017).
Ocelic, N., Huber, A. & Hillenbrand, R. Pseudoheterodyne detection for background-free near-field spectroscopy. Appl. Phys. Lett. 89, 101124 (2006).
We acknowledge discussions with A. Tredicucci about the general concept and S. Wall about the experimental measurement technique. We also thank A. Govyadinov for discussions about the thin-film inversion model. P.S. acknowledges financial support by a scholarship from the ‘la Caixa’ Banking Foundation. F.V. acknowledges financial support from Marie-Curie International Fellowship COFUND and ICFOnest programme. M.M. thanks the Natural Sciences and Engineering Research Council of Canada (PGSD3-426325-2012). K.-J.T. acknowledges support from a Mineco Young Investigator Grant (FIS2014-59639-JIN). F.H.L.K. acknowledges financial support from the Government of Catalonia through an SGR grant (2014-SGR-1535), and from the Spanish Ministry of Economy and Competitiveness through the ‘Severo Ochoa’; Programme for Centres of Excellence in R&D (SEV-2015-0522), support by the Fundacio Cellex Barcelona, CERCA Programme/Generalitat de Catalunya and the Mineco grants Ramón y Cajal (RYC-2012-12281) and Plan Nacional (FIS2013-47161-P and FIS2014-59639-JIN). Furthermore, the research leading to these results received funding from the European Union Seventh Framework Programme under grant agreement no. 696656 Graphene Flagship, European Reasearch Council (ERC) Starting grant (307806, CarbonLight) and ERC Synergy Grant Hetero2D. K.S.T. acknowledges financial support from The Center for Nanostructured Graphene sponsored by the Danish National Research Foundation (Project DNRF103) and the ERC under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 773122, LIMA).
R.H. is cofounder of and on the scientific advisory board of Neaspec GmbH, a company that produces scattering-type near-field scanning optical microscope systems, such as the one used in this study. The remaining authors declare no competing interests.
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Schmidt, P., Vialla, F., Latini, S. et al. Nano-imaging of intersubband transitions in van der Waals quantum wells. Nature Nanotech 13, 1035–1041 (2018). https://doi.org/10.1038/s41565-018-0233-9
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