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.

Artificial charge-modulationin atomic-scale perovskite titanate superlattices

Abstract

The nature and length scales of charge screening in complex oxides are fundamental to a wide range of systems, spanning ceramic voltage-dependent resistors (varistors), oxide tunnel junctions and charge ordering in mixed-valence compounds1,2,3,4,5,6. There are wide variations in the degree of charge disproportionation, length scale, and orientation in the mixed-valence compounds: these have been the subject of intense theoretical study7,8,9,10,11, but little is known about the microscopic electronic structure. Here we have fabricated an idealized structure to examine these issues by growing atomically abrupt layers of LaTi3+O3 embedded in SrTi4+O3. Using an atomic-scale electron beam, we have observed the spatial distribution of the extra electron on the titanium sites. This distribution results in metallic conductivity, even though the superlattice structure is based on two insulators. Despite the chemical abruptness of the interfaces, we find that a minimum thickness of five LaTiO3 layers is required for the centre titanium site to recover bulk-like electronic properties. This represents a framework within which the short-length-scale electronic response can be probed and incorporated in thin-film oxide heterostructures.

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

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Annular dark field (ADF) image of LaTiO3 layers (bright) of varying thickness spaced by SrTiO3 layers.
Figure 2: Electron energy-loss spectra (EELS) for La and Ti simultaneously recorded across a 2-unit-cell LaTiO3 layer in SrTiO3.
Figure 3: Spatial distribution of the Ti3+ signal in the vicinity of the LaTiO3 layer and bilayer.
Figure 4: Summary of the electronic properties in SrTiO3/LaTiO3 superlattices as a function of the number of LaTiO3 unit cells.

References

  1. Greuter, F. & Blatter, G. Electrical properties of grain boundaries in polycrystalline compound semiconductors. Semicond. Sci. Technol. 5, 111–137 (1990)

    Article  ADS  CAS  Google Scholar 

  2. Chaudhari, P. et al. Direct measurement of the superconducting properties of single grain boundaries in Y1Ba2Cu3O7-δ . Phys. Rev. Lett. 60, 1653–1656 (1988)

    Article  ADS  CAS  Google Scholar 

  3. Sun, J. Z. et al. Observation of large low-field magnetoresistance in trilayer perpendicular transport devices made using doped manganate perovskites. Appl. Phys. Lett. 69, 3266–3268 (1996)

    Article  ADS  CAS  Google Scholar 

  4. Chen, C. H., Cheong, S-W. & Cooper, A. S. Charge modulations in La2-xSrxNiO4+y: ordering of polarons. Phys. Rev. Lett. 71, 2461–2464 (1993)

    Article  ADS  CAS  Google Scholar 

  5. Tranquada, J. M., Sternlieb, B. J., Axe, J. D., Nakamura, Y. & Uchida, S. Evidence for stripe correlations of spins and holes in copper oxide superconductors. Nature 375, 561–563 (1995)

    Article  ADS  Google Scholar 

  6. Mori, S., Chen, C. H. & Cheong, S-W. Pairing of charge-ordered stripes in (La,Ca)MnO3 . Nature 392, 473–476 (1998)

    Article  ADS  CAS  Google Scholar 

  7. Zaanen, J. & Gunnarsson, O. Charged magnetic domain lines and the magnetism of high-Tc oxides. Phys. Rev. B 40, 7391–7394 (1989)

    Article  ADS  CAS  Google Scholar 

  8. Poilblanc, D. & Rice, T. M. Charged solitons in the Hartree-Fock approximation to the large-U Hubbard model. Phys. Rev. B 39, 9749–9752 (1989)

    Article  ADS  CAS  Google Scholar 

  9. Inui, M. & Littlewood, P. B. Hartree-Fock study of the magnetism in the single-band Hubbard model. Phys. Rev. B 44, 4415–4422 (1991)

    Article  ADS  CAS  Google Scholar 

  10. Loew, U., Emery, V. J., Fabricius, K. & Kivelson, S. A. Study of an Ising model with competing long- and short-range interactions. Phys. Rev. Lett. 72, 1918–1921 (1994)

    Article  ADS  CAS  Google Scholar 

  11. Kivelson, S. A., Fradkin, E. & Emery, V. J. Electronic liquid-crystal phases of a doped Mott insulator. Nature 393, 550–553 (1998)

    Article  ADS  CAS  Google Scholar 

  12. Tokura, Y. et al. Filling dependence of electronic properties on the verge of metal-Mott-insulator transitions in Sr1-xLaxTiO3 . Phys. Rev. Lett. 70, 2126–2129 (1993)

    Article  ADS  CAS  Google Scholar 

  13. Sunstrom, J. E. IV, Kauzlarich, S. M. & Klavins, P. Synthesis, structure, and properties of La1-xSrxTiO3 (0 ≤ x ≤ 1). Chem. Mater. 4, 346–353 (1992)

    Article  CAS  Google Scholar 

  14. Kahn, A. H. & Leyendecker, A. J. Electronic energy bands in strontium titanate. Phys. Rev. 135, A1321–A1325 (1964)

    Article  ADS  Google Scholar 

  15. Ohtomo, A., Muller, D. A., Grazul, J. L. & Hwang, H. Y. Epitaxial growth and electronic structure of LaTiOx films. Appl. Phys. Lett. 80, 3922–3924 (2002)

    Article  ADS  CAS  Google Scholar 

  16. Kawasaki, M. et al. Atomic control of the SrTiO3 crystal surface. Science 266, 1540–1542 (1994)

    Article  ADS  CAS  Google Scholar 

  17. Howie, A. Image contrast and localized signal selection techniques. J. Microsc. 17, 11–23 (1979)

    Article  Google Scholar 

  18. Pennycook, S. J. Z contrast STEM for materials science. Ultramicroscopy 30, 58–69 (1989)

    Article  Google Scholar 

  19. Kirkland, E. J., Loane, R. F. & Silcox, J. Simulation of annular dark field STEM images using a modified multislice method. Ultramicroscopy 23, 77–96 (1987)

    Article  Google Scholar 

  20. Batson, P. E. Simultaneous STEM imaging and electron energy-loss spectroscopy with atomic column sensitivity. Nature 366, 727–728 (1993)

    Article  ADS  CAS  Google Scholar 

  21. Muller, D. A., Tzou, Y., Raj, R. & Silcox, J. Mapping sp2 and sp3 states of carbon at sub-nanometre spatial resolution. Nature 366, 725–727 (1993)

    Article  ADS  CAS  Google Scholar 

  22. Browning, N. D., Chisholm, M. M. & Pennycook, S. J. Atomic-resolution chemical analysis using a scanning transmission electron microscope. Nature 366, 143–146 (1993)

    Article  ADS  CAS  Google Scholar 

  23. Zaanen, J., Sawatzky, G. A. & Allen, J. W. Band gaps and electronic structure of transition-metal compounds. Phys. Rev. Lett. 55, 418–421 (1985)

    Article  ADS  CAS  Google Scholar 

  24. Abbate, M. et al. Soft-x-ray-absorption studies of the location of extra charges induced by substitution in controlled-valence materials. Phys. Rev. B 44, 5419–5422 (1991)

    Article  ADS  CAS  Google Scholar 

  25. Taguchi, Y. et al. Critical behaviour in LaTiO3+δ/2 in the vicinity of antiferromagnetic instability. Phys. Rev. B 59, 7917–7924 (1999)

    Article  ADS  CAS  Google Scholar 

Download references

Acknowledgements

We thank G. E. Blumberg, R. de Picciotto, B. I. Halperin, D. R. Hamann, S. H. Simon, C. M. Varma and N. Zhitenev for discussions. A.O. acknowledges partial support by the Nishina Memorial Foundation, Japan.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to H. Y. Hwang.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Ohtomo, A., Muller, D., Grazul, J. et al. Artificial charge-modulationin atomic-scale perovskite titanate superlattices. Nature 419, 378–380 (2002). https://doi.org/10.1038/nature00977

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature00977

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

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