Skip to main content

Thank you for visiting 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.

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


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.

Your institute does not have access to this article

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Structural and morphological characterization of LAO/STO structures.
Figure 2: Schematic diagram of the CT-AFM experiment.
Figure 3: ‘Non-annealed’ LAO/STO interface.
Figure 4: ‘In situ annealed’ LAO/STO interface.
Figure 5: Nanoscale CT-AFM characterization of carrier distribution across LAO/STO interfaces.


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

    CAS  Article  Google Scholar 

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

    Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  4. Thiel, S., Hammerl, G., Schmehl, A., Schneider, C. W. & Mannhart, J. Tunable quasi–two-dimensional electron gases in oxide heterostructures. Science 313, 1942–1946 (2006).

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  6. Frederikse, H. P. R. & Hosler, W. R. Hall mobility in SrTiO3 . Phys. Rev. 161, 822–827 (1967).

    CAS  Article  Google Scholar 

  7. Koonce, C. S., Cohen, M. L., Schooley, J. F., Hosler, W. R. & Pfeiffer, E. R. Superconducting transition temperatures of semiconducting SrTiO3 . Phys. Rev. 163, 380–390 (1967).

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  9. Ueda, K., Tabata, H. & Kawai, T. Ferromagnetism in LaFeO3/LaCrO3 superlattices. Science 280, 1064–1066 (1998).

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  11. Nakagawa, N., Hwang, H. Y. & Muller, D. A. Why some interfaces cannot be sharp. Nature Mater. 5, 204–209 (2006).

    CAS  Article  Google Scholar 

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

    Article  Google Scholar 

  13. Park, M. S., Rhim, S. H. & Freeman, A. J. Charge compensation and mixed valency in LaAlO3/SrTiO3 heterointerfaces studied by the FLAPW method. Phys. Rev. B 74, 205416 (2006).

    Article  Google Scholar 

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

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

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

    Article  Google Scholar 

  17. Kalabukhov, A. S. 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).

    Article  Google Scholar 

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

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  21. Ishigaki, T., Yamauchi, S., Kishio, K., Mizusaki, J. & Fueki, K. Diffusion of oxide ion vacancies in perovskite-type oxides. J. Solid State Chem. 73, 179–187 (1988).

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  23. Maurice, J.-L. 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).

    Article  Google Scholar 

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

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  26. Houzé, F., Meyer, R., Schneegans, O. & Boyer, L. Imaging the local electrical properties of metal surfaces by atomic force microscopy with conducting probes. Appl. Phys. Lett. 69, 1975–1977 (1996).

    Article  Google Scholar 

Download references


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.

Author information

Authors and Affiliations


Corresponding authors

Correspondence to G. Herranz or A. Barthélémy.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Basletic, M., Maurice, JL., Carrétéro, C. et al. Mapping the spatial distribution of charge carriers in LaAlO3/SrTiO3 heterostructures. Nature Mater 7, 621–625 (2008).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Further reading


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