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Epitaxial SrTiO3 films with electron mobilities exceeding 30,000 cm2 V−1 s−1

Nature Materials volume 9, pages 482–484 (2010)Cite this article

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Abstract

The study of quantum phenomena in semiconductors requires epitaxial structures with exceptionally high charge-carrier mobilities1. Furthermore, low-temperature mobilities are highly sensitive probes of the quality of epitaxial layers, because they are limited by impurity and defect scattering. Unlike many other complex oxides, electron-doped SrTiO3 single crystals show high (∼104 cm2 V−1 s−1) electron mobilities at low temperatures. High-mobility, epitaxial heterostructures with SrTiO3 have recently attracted attention for thermoelectric applications2, field-induced superconductivity3 and two-dimensional (2D) interface conductivity4. Epitaxial SrTiO3 thin films are often deposited by energetic techniques, such as pulsed laser deposition. Electron mobilities in such films are lower than those of single crystals5. In semiconductor physics, molecular beam epitaxy (MBE) is widely established as the deposition method that produces the highest mobility structures1,6,7. It is a low-energetic, high-purity technique that allows for low defect densities and precise control over doping concentrations and location. Here, we demonstrate controlled doping of epitaxial SrTiO3 layers grown by MBE. Electron mobilities in these films exceed those of single crystals. At low temperatures, the films show Shubnikov–de Haas oscillations. These high-mobility SrTiO3 films allow for the study of the intrinsic physics of SrTiO3 and can serve as building blocks for high-mobility oxide heterostructures.

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Figure 1: Carrier concentrations of SrTiO3 films as a function of La-dopant concentration.
Figure 2: Carrier concentrations and electron mobilities of homoepitaxial SrTiO3 thin films.
Figure 3: SdH oscillations in homoepitaxial SrTiO3 thin films.

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Acknowledgements

The authors thank J. Allen for many useful discussions and T. Mates for help with the SIMS measurements. The work was supported by the US Department of Energy, Basic Energy Sciences (grant no. DE-FG02-02ER45994). O.B. is supported by a grant from the AFSOR (Award #FA9550-08-1-0461—K. Reinhardt, programme manager). B.J. is supported by the UCSB MRL (National Science Foundation award No. DMR 05-20415). This work made use of the MRL Central facilities supported by the MRSEC Program of the National Science Foundation under award No. DMR 05-20415 and of the UCSB Nanofabrication Facility, a part of the NSF-funded NNIN network.

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  1. Junwoo Son, Pouya Moetakef, Bharat Jalan and Oliver Bierwagen: These authors contributed equally to this work

Authors and Affiliations

  1. Materials Department, University of California, Santa Barbara, California 93106-5050, USA

    Junwoo Son, Pouya Moetakef, Bharat Jalan, Oliver Bierwagen, Nicholas J. Wright, Roman Engel-Herbert & Susanne Stemmer

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  1. Junwoo Son
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  2. Pouya Moetakef
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Contributions

B.J. developed the MBE growth process and P.M. grew the films. J.S. and O.B. carried out the transport measurements and data analysis. N.J.W. and R.E.-H. helped with the MBE growth experiments. S.S. assisted with the planning and analysis of the study.

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Correspondence to Bharat Jalan or Susanne Stemmer.

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Son, J., Moetakef, P., Jalan, B. et al. Epitaxial SrTiO3 films with electron mobilities exceeding 30,000 cm2 V−1 s−1. Nature Mater 9, 482–484 (2010). https://doi.org/10.1038/nmat2750

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