The structure and chemistry of the TiO2-rich surface of SrTiO3 (001)

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Abstract

Oxide surfaces are important for applications in catalysis and thin film growth. An important frontier in solid-state inorganic chemistry is the prediction of the surface structure of an oxide. Comparatively little is known about atomic arrangements at oxide surfaces at present, and there has been considerable discussion concerning the forces that control such arrangements. For instance, one model suggests that the dominant factor is a reduction of Coulomb forces1; another favours minimization of ‘dangling bonds’ by charge transfer to states below the Fermi energy2. The surface structure and properties of SrTiO3—a standard model for oxides with a perovskite structure—have been studied extensively3,4,5,6,7,8,9,10,11,12,13,14. Here we report a solution of the 2 × 1 SrTiO3 (001) surface structure obtained through a combination of high-resolution electron microscopy and theoretical direct methods. Our results indicate that surface rearrangement of TiO6-x units into edge-sharing blocks determines the SrO-deficient surface structure of SrTiO3. We suggest that this structural concept can be extended to perovskite surfaces in general.

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Figure 1: Bright-field image and off-zone-axis diffraction pattern (inset) of the (2 × 1) SrTiO3 (001) surface, taken using the UHV-H9000 Hitachi transmission electron microscope (TEM).
Figure 2: High-resolution image of the 2 × 1 SrTiO3 (001) surface.
Figure 3: Theoretical direct methods solution of the (2 × 1) structure.
Figure 4: The 2 × 1 SrTiO3 (001) surface structure.

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Acknowledgements

HREM analysis was carried out at the Electron Microscopy Collaborative Research Center at Argonne National Laboratory. This work was supported by the EMSI program of the National Science Foundation and the US Department of Energy Office of Science at the Northwestern University Institute for Environmental Catalysis. M.A. acknowledges funding from the National Science Foundation.

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Correspondence to Laurence D. Marks.

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Erdman, N., Poeppelmeier, K., Asta, M. et al. The structure and chemistry of the TiO2-rich surface of SrTiO3 (001). Nature 419, 55–58 (2002) doi:10.1038/nature01010

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