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Mapping the spatial distribution of charge carriers in LaAlO3/SrTiO3 heterostructures

Nature Materials volume 7, pages 621625 (2008) | Download Citation



At the interface between complex insulating oxides, novel phases with interesting properties may occur, such as the metallic state reported in the LaAlO3/SrTiO3 system 1. Although this state has been predicted 2 and reported3,4 to be confined at the interface, some studies indicate a much broader spatial extension5, thereby questioning its origin. Here, we provide for the first time a direct determination of the carrier density profile of this system through resistance profile mappings collected in cross-section LaAlO3/SrTiO3 samples with a conducting-tip atomic force microscope (CT-AFM). We find that, depending on specific growth protocols, the spatial extension of the high-mobility electron gas can be varied from hundreds of micrometres into SrTiO3 to a few nanometres next to the LaAlO3/SrTiO3 interface. Our results emphasize the potential of CT-AFM as a novel tool to characterize complex oxide interfaces and provide us with a definitive and conclusive way to reconcile the body of experimental data in this system.

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  1. 1.

    & A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface. Nature 427, 423–426 (2004).

  2. 2.

    & Charge localization or itineracy at LaAlO3/STiO3 interfaces: Hole polarons, oxygen vacancies, and mobile electrons. Phys. Rev. B 74, 035112 (2006).

  3. 3.

    et al. Electronically coupled complementary interfaces between perovskite band insulators. Nature Mater. 5, 556–560 (2006).

  4. 4.

    , , , & Tunable quasi–two-dimensional electron gases in oxide heterostructures. Science 313, 1942–1946 (2006).

  5. 5.

    et al. High mobility in LaAlO3/SrTiO3 heterostructures: Origin, dimensionality, and perspectives. Phys. Rev. Lett. 98, 216803 (2007).

  6. 6.

    & Hall mobility in SrTiO3. Phys. Rev. 161, 822–827 (1967).

  7. 7.

    , , , & Superconducting transition temperatures of semiconducting SrTiO3. Phys. Rev. 163, 380–390 (1967).

  8. 8.

    et al. Enhanced dielectric properties of SrTiO3 epitaxial thin films for tunable microwave devices. Appl. Phys. Lett. 80, 109–111 (2002).

  9. 9.

    , & Ferromagnetism in LaFeO3/LaCrO3 superlattices. Science 280, 1064–1066 (1998).

  10. 10.

    et al. Quantum Hall effect in polar oxide heterostructures. Science 315, 1388–1391 (2007).

  11. 11.

    , & Why some interfaces cannot be sharp. Nature Mater. 5, 204–209 (2006).

  12. 12.

    et al. Origin of charge density at LaAlO3 on SrTiO3 heterointerfaces: Possibility of intrinsic doping. Phys. Rev. Lett. 98, 196802 (2007).

  13. 13.

    , & Charge compensation and mixed valency in LaAlO3/SrTiO3 heterointerfaces studied by the FLAPW method. Phys. Rev. B 74, 205416 (2006).

  14. 14.

    et al. Electronic conductivity and structural distortion at the interface between insulators SrTiO3 and LaAlO3. Phys. Status Solidi A 203, 2209–2214 (2006).

  15. 15.

    et al. Photoemission (XPS and XPD) study of epitaxial LaAlO3 film grown on SrTiO3(001). Mater. Sci. Semicond. Process. 9, 954–958 (2006).

  16. 16.

    et al. Interface structure of SrTiO3/LaAlO3 at elevated temperatures studied in situ by synchrotron X rays. Phys. Rev. B 75, 235417 (2007).

  17. 17.

    et al. Effect of oxygen vacancies in the SrTiO3 substrate on the electrical properties of the LaAlO3/SrTiO3 interface. Phys. Rev. B 75, 121404(R) (2007).

  18. 18.

    et al. Nanoscale control of an interfacial metal–insulator transition at room temperature. Nature Mater. 7, 298–302 (2008).

  19. 19.

    et al. Superconducting interfaces between insulating oxides. Science 317, 1196–1199 (2007).

  20. 20.

    et al. Magnetic effects at the interface between non-magnetic oxides. Nature Mater. 6, 493–496 (2007).

  21. 21.

    , , , & Diffusion of oxide ion vacancies in perovskite-type oxides. J. Solid State Chem. 73, 179–187 (1988).

  22. 22.

    et al. Charge imbalance at oxide interfaces: How nature deals with it. Mater. Sci. Eng. B 144, 1–6 (2007).

  23. 23.

    et al. Electron energy loss spectroscopy determination of Ti oxidation state at the (001) LaAlO3/SrTiO3 interface as a function of LaAlO3 growth conditions. Europhys. Lett. 82, 17003 (2008).

  24. 24.

    Oxide interfaces: Watch out for the lack of oxygen. Nature Mater. 6, 473–474 (2007).

  25. 25.

    et al. Structural basis for the conducting interface between LaAlO3 and SrTiO3. Phys. Rev. Lett. 99, 155502 (2007).

  26. 26.

    , , & Imaging the local electrical properties of metal surfaces by atomic force microscopy with conducting probes. Appl. Phys. Lett. 69, 1975–1977 (1996).

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G.H. acknowledges financial support from the DURSI (Generalitat de Catalunya, Spain). Financial support from PAI- France-Croatia COGITO Program No. 82/240083, Croatian MZOS Project No. 119-1191458-1023 and the French Agence Nationale de la Recherche (Project Pnano ALICANTE) is acknowledged. We thank Y. Gourdel for his help in the polishing process. The authors acknowledge J. N. Eckstein for valuable comments.

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    • M. Basletic
    •  & G. Herranz

    Current address: Department of Physics, Faculty of Science, University of Zagreb, HR-10002 Zagreb, Croatia (M.B.); Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de la UAB, Bellaterra 08193, Catalonia, Spain (G.H.)


  1. Unité Mixte de Physique CNRS/Thales, Associée à l’Université Paris-Sud, Route départementale 128, 91767 Palaiseau Cedex, France


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Correspondence to G. Herranz or A. Barthélémy.

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