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Electric polarization switching in an atomically thin binary rock salt structure

Nature Nanotechnologyvolume 13pages1923 (2018) | Download Citation


Inducing and controlling electric dipoles is hindered in the ultrathin limit by the finite screening length of surface charges at metal–insulator junctions1,2,3, although this effect can be circumvented by specially designed interfaces4. Heterostructures of insulating materials hold great promise, as confirmed by perovskite oxide superlattices with compositional substitution to artificially break the structural inversion symmetry5,6,7,8. Bringing this concept to the ultrathin limit would substantially broaden the range of materials and functionalities that could be exploited in novel nanoscale device designs. Here, we report that non-zero electric polarization can be induced and reversed in a hysteretic manner in bilayers made of ultrathin insulators whose electric polarization cannot be switched individually. In particular, we explore the interface between ionic rock salt alkali halides such as NaCl or KBr and polar insulating Cu2N terminating bulk copper. The strong compositional asymmetry between the polar Cu2N and the vacuum gap breaks inversion symmetry in the alkali halide layer, inducing out-of-plane dipoles that are stabilized in one orientation (self-poling). The dipole orientation can be reversed by a critical electric field, producing sharp switching of the tunnel current passing through the junction.

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  1. 1.

    Junquera, J. & Ghosez, P. Critical thickness for ferroelectricity in perovskite ultrathin films. Nature 422, 506–509 (2003).

  2. 2.

    Kim, D. J. et al. Polarization relaxation induced by a depolarization field in ultrathin ferroelectric BaTiO3 capacitors. Phys. Rev. Lett. 95, 237602 (2005).

  3. 3.

    Stengel, M. et al. Origin of the dielectric dead layer in nanoscale capacitors. Nature 443, 679–682 (2006).

  4. 4.

    Stengel, M. et al. Enhancement of ferroelectricity at metal–oxide interfaces. Nat. Mater. 8, 392–397 (2009).

  5. 5.

    Sai, N. et al. Compositional inversion symmetry breaking in ferroelectric perovskites. Phys. Rev. Lett. 84, 5636–5639 (2000).

  6. 6.

    Rogdakis, K. et al. Tunable ferroelectricity in artificial tri-layer superlattices comprised of non-ferroic components. Nat. Commun. 3, 1064 (2012).

  7. 7.

    Warusawithana, M. P., Colla, E. V., Eckstein, J. N. & Weissman, M. B. Artificial dielectric superlattices with broken inversion symmetry. Phys. Rev. Lett. 90, 036802 (2003).

  8. 8.

    Lee, H. N. et al. Strong polarization enhancement in asymmetric three-component ferroelectric superlattices. Nature. 433, 395–399 (2005).

  9. 9.

    Nilius, M., Wallis, T. M. & Ho, W. Influence of a heterogeneous Al2O3 surface on the electronic properties of single Pd atoms. Phys. Rev. Lett. 90, 046808 (2003).

  10. 10.

    Rau, I. G. et al. Reaching the magnetic anisotropy limit of a 3d metal atom. Science 344, 988–992 (2014).

  11. 11.

    Leibsle, F. M., Dhesi, S. S., Barrett, S. D. & Robinson, A. W. STM observations of Cu(100)−c(2×2)N surfaces: evidence for attractive interactions and an incommensurate c(2×2)structure. Surf. Sci. 317, 309–320 (1994).

  12. 12.

    Hirjibehedin, C. F. et al. Large magnetic anisotropy of a single atomic spin embedded in a surface molecular network. Science 317, 1199–1203 (2007).

  13. 13.

    Repp, J., Meyer, G., Olsson, F. E. & Persson, M. Controlling the charge state of individual gold adatoms. Science 305, 493–495 (2004).

  14. 14.

    Chang, K. et al. Discovery of robust in-plane ferroelectricity in atomic thick SnTe. Science 353, 274–278 (2016).

  15. 15.

    Hebenstreit, W. et al. Atomic resolution by STM on ultra-thin films of alkali halides: experiment and local density calculations. Surf. Sci. 424, L321–L328 (1999).

  16. 16.

    Choi, T., Ruggiero, C. D. & Gupta, J. A. Incommensurability and atomic structure of c(2×2)N/Cu(100): a scanning tunneling microscopy study. Phys. Rev. B 78, 035430 (2008).

  17. 17.

    Ruggiero, C. D., Choi, T. & Gupta, J. A. Tunneling spectroscopy of ultrathin insulating films: CuN on Cu(100). Appl. Phys. Lett. 91, 253106 (2007).

  18. 18.

    Qiu, X. H., Nazin, G. V. & Ho, W. Mechanisms of reversible conformational transitions in a single molecule. Phys. Rev. Lett. 93, 196806 (2004).

  19. 19.

    Leung, T. C. et al. Relationship between surface dipole, work function and charge transfer: some exceptions to an established rule. Phys. Rev. B 68, 195408 (2003).

  20. 20.

    Gajek, M. et al. Tunnel junctions with multiferroic barriers. Nat. Mater. 6, 296–302 (2007).

  21. 21.

    Garcia, V. et al. Giant tunnel electroresistane for non-destructive readout of ferroelectric states. Nature 460, 81–84 (2009).

  22. 22.

    Kohlstedt, H., Pertsev, N. A., Rodriguez Contreras, J. & Waser, R. Theoretical current–voltage characteristics of ferroelectric tunnel junctions. Phys. Rev. B 72, 125341 (2005).

  23. 23.

    Giessibl, F. J. Advances in atomic force microscopy. Rev. Mod. Phys. 75, 949–983 (2003).

  24. 24.

    de la Torre, Betal Atomic-scale variations of the mechanical response of 2D materials detected by noncontact atomic force microscopy. Phys. Rev. Lett. 116, 245502 (2016).

  25. 25.

    Schuler, B. et al. Effect of electron–phonon interaction on the formation of one-dimensional electronic states in coupled Cl vacancies. Phys. Rev. B 91, 235443 (2015).

  26. 26.

    Lee, D. et al. Emergence of room-temperature ferroelectricity at reduced dimensions. Science 349, 1314–1317 (2015).

  27. 27.

    Costanzo, D. et al. Gate-induced superconductivity in atomically thin MoS2 crystals. Nat. Nanotech. 11, 339–344 (2016).

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The authors thank P. Zubko for stimulating discussions. J.M.-C. and C.F.H. acknowledge financial support from Specs GmbH and EPSRC (EP/H002367/1). D.S. and M.Pi. acknowledge funding from Specs GmbH, MINECO (MAT2013-46593-C6-3-P),and the use of SAI-Universidad de Zaragoza. M.Pe. acknowledges computer time allocated on ARCHER through the Materials Chemistry Consortium funded by an EPSRC grant (EP/L000202), on Polaris through N8 HPC funded by an EPSRC grant(EP/K000225/1) and on Chadwick at the University of Liverpool.

Author information

Author notes

    • Jose Martinez-Castro

    Present address: Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva 4, Switzerland


  1. London Centre for Nanotechnology, University College London (UCL), London, WC1H 0AH, UK

    • Jose Martinez-Castro
    •  & Cyrus F. Hirjibehedin
  2. Department of Physics & Astronomy, UCL, London, WC1E 6BT, UK

    • Jose Martinez-Castro
    •  & Cyrus F. Hirjibehedin
  3. Instituto de Nanociencia de Aragón and Laboratorio de Microscopías Avanzadas, Universidad de Zaragoza, 50018, Zaragoza, Spain

    • Jose Martinez-Castro
    • , Marten Piantek
    • , Sonja Schubert
    •  & David Serrate
  4. Fundación Instituto de Nanociencia de Aragón (FINA), 50018, Zaragoza, Spain

    • Marten Piantek
    •  & David Serrate
  5. Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009, Zaragoza, Spain

    • Marten Piantek
    • , Sonja Schubert
    •  & David Serrate
  6. Surface Science Research Centre and Department of Chemistry, University of Liverpool, Liverpool, L69 3BX, UK

    • Mats Persson
  7. Department of Physics, Chalmers University of Technology, SE-412 96, Göteborg, Sweden

    • Mats Persson
  8. Department of Chemistry, UCL, London, WC1H 0AJ, UK

    • Cyrus F. Hirjibehedin


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J.M.-C., D.S. and C.F.H. conceived of the project. J.M.-C., M.Pi., S.S. and D.S. performed the experiments and analysed the results. M.Pe. performed the DFT calculations.All authors discussed the results and contributed to the writing of the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to David Serrate or Cyrus F. Hirjibehedin.

Electronic supplementary material

  1. Supplementary Information

    Supplementary Methods, Supplementary Table 1.

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