Mapping the spatial distribution of charge carriers in LaAlO3/SrTiO3 heterostructures
Source abstract
Abstract
At the interface between complex insulating oxides, novel phases with interesting properties may occur, such as the metallic state reported in the LaAlO(3)/SrTiO(3) system . Although this state has been predicted and reported to be confined at the interface, some studies indicate a much broader spatial extension, 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 LaAlO(3)/SrTiO(3) 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 SrTiO(3) to a few nanometres next to the LaAlO(3)/SrTiO(3) 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.
Source: europepmc · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: Electronic and Structural Properties of Oxides · Advanced X-ray and CT Imaging · Magnetic and transport properties of perovskites and related materials
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (26)
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1. Ohtomo, A. & Hwang, H. Y. A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface. Nature 427, 423–426 (2004).10.1038/nature02308 ↗
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).10.1103/PhysRevB.74.035112 ↗
3. Huijben, M. et al. Electronically coupled complementary interfaces between perovskite band insulators. Nature Mater. 5, 556–560 (2006).10.1038/nmat1675 ↗
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).10.1126/science.1131091 ↗
5. Herranz, G. et al. High mobility in LaAlO3/SrTiO3 heterostructures: Origin, dimensionality, and perspectives. Phys. Rev. Lett. 98, 216803 (2007).10.1103/PhysRevLett.98.216803 ↗
6. Frederikse, H. P. R. & Hosler, W. R. Hall mobility in SrTiO3 . Phys. Rev. 161, 822–827 (1967).10.1103/PhysRev.161.822 ↗
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).10.1103/PhysRev.163.380 ↗
8. Bouzehouane, K. et al. Enhanced dielectric properties of SrTiO3 epitaxial thin films for tunable microwave devices. Appl. Phys. Lett. 80, 109–111 (2002).10.1063/1.1428411 ↗
9. Ueda, K., Tabata, H. & Kawai, T. Ferromagnetism in LaFeO3/LaCrO3 superlattices. Science 280, 1064–1066 (1998).10.1126/science.280.5366.1064 ↗
10. Tsukazaki, A. et al. Quantum Hall effect in polar oxide heterostructures. Science 315, 1388–1391 (2007).10.1126/science.1137430 ↗
11. Nakagawa, N., Hwang, H. Y. & Muller, D. A. Why some interfaces cannot be sharp. Nature Mater. 5, 204–209 (2006).10.1038/nmat1569 ↗
12. Siemons, W. et al. Origin of charge density at LaAlO3 on SrTiO3 heterointerfaces: Possibility of intrinsic doping. Phys. Rev. Lett. 98, 196802 (2007).10.1103/PhysRevLett.98.196802 ↗
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).10.1103/PhysRevB.74.205416 ↗
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).10.1002/pssa.200566033 ↗
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).10.1016/j.mssp.2006.10.044 ↗
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).10.1103/PhysRevB.75.235417 ↗
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).10.1103/PhysRevB.75.121404 ↗
18. Cen, C et al. Nanoscale control of an interfacial metal–insulator transition at room temperature. Nature Mater. 7, 298–302 (2008).10.1038/nmat2136 ↗
19. Reyren, N. et al. Superconducting interfaces between insulating oxides. Science 317, 1196–1199 (2007).10.1126/science.1146006 ↗
20. Brinkman, A. et al. Magnetic effects at the interface between non-magnetic oxides. Nature Mater. 6, 493–496 (2007).10.1038/nmat1931 ↗
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).10.1016/0022-4596(88)90067-9 ↗
22. Maurice, J.-L. et al. Charge imbalance at oxide interfaces: How nature deals with it. Mater. Sci. Eng. B 144, 1–6 (2007).10.1016/j.mseb.2007.07.095 ↗
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).10.1209/0295-5075/82/17003 ↗
24. Eckstein, J. Oxide interfaces: Watch out for the lack of oxygen. Nature Mater. 6, 473–474 (2007).10.1038/nmat1944 ↗
25. Willmott, P. R. et al. Structural basis for the conducting interface between LaAlO3 and SrTiO3 . Phys. Rev. Lett. 99, 155502 (2007).10.1103/PhysRevLett.99.155502 ↗
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).10.1063/1.117179 ↗