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Transition from Reconstruction toward Thin Film on the (110) Surface of Strontium Titanate.

Wang Z, Loon A, Subramanian A, Gerhold S, McDermott E, Enterkin JA, Hieckel M, Russell BC, Green RJ, Moewes A, Guo J, Blaha P, Castell MR, Diebold U, Marks LD - Nano Lett. (2016)

Bottom Line: Such structures can also be viewed as ultrathin films, epitaxed on a substrate.Whereas SrTiO3 (110) invariably terminates with an overlayer of titania, with increasing density its structure switches from n × 1 to 2 × n.At the same time the coordination of the Ti atoms changes from a network of corner-sharing tetrahedra to a double layer of edge-shared octahedra with bridging units of octahedrally coordinated strontium.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Physics, TU Wien , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria.

ABSTRACT
The surfaces of metal oxides often are reconstructed with a geometry and composition that is considerably different from a simple termination of the bulk. Such structures can also be viewed as ultrathin films, epitaxed on a substrate. Here, the reconstructions of the SrTiO3 (110) surface are studied combining scanning tunneling microscopy (STM), transmission electron diffraction, and X-ray absorption spectroscopy (XAS), and analyzed with density functional theory calculations. Whereas SrTiO3 (110) invariably terminates with an overlayer of titania, with increasing density its structure switches from n × 1 to 2 × n. At the same time the coordination of the Ti atoms changes from a network of corner-sharing tetrahedra to a double layer of edge-shared octahedra with bridging units of octahedrally coordinated strontium. This transition from the n × 1 to 2 × n reconstructions is a transition from a pseudomorphically stabilized tetrahedral network toward an octahedral titania thin film with stress-relief from octahedral strontia units at the surface.

No MeSH data available.


Related in: MedlinePlus

Convex-hullconstruction (red) of the surface enthalpies in eV/1 × 1 (y-axis) for different TiO2 excess per 1 ×1 unit cell (x-axis), revTP SSh functional. Errorbars are 0.1 eV/1 × 1 cell. Lines are shown for the 2 × na and 2 × nb families, as well asthe 2-phase coexistence (blue dashes) between the 3 × 1 and 2× 4a structures observed for the samples preparedat higher temperatures.13
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fig4: Convex-hullconstruction (red) of the surface enthalpies in eV/1 × 1 (y-axis) for different TiO2 excess per 1 ×1 unit cell (x-axis), revTP SSh functional. Errorbars are 0.1 eV/1 × 1 cell. Lines are shown for the 2 × na and 2 × nb families, as well asthe 2-phase coexistence (blue dashes) between the 3 × 1 and 2× 4a structures observed for the samples preparedat higher temperatures.13

Mentions: The DFT convex-hull is shown in Figure 4 with error-barsof 0.1 eV/1 × 1 cell. This is a conventional representation ofthe energetics versus composition, and here the enthalpy versus surfaceexcess of TiO2. The lower envelope describes the singleor two-phase coexistence regimes as a function of surface composition.The 2 × na family occur at lower surface excessof TiO2, consistent with coexistence with n × 1 reconstructions for the high-temperature samples.13 At the high TiO2 coverage (right)of the convex hull both 2 × n families are convergingto a straight line to a nominal 2 × ∞ structure (see Supporting Information CIF file). For a straightline, one expects extensive coexistence of structures due to the entropyof mixing similar to that found for the (111) surface,12 which is consistent with the experimental results.


Transition from Reconstruction toward Thin Film on the (110) Surface of Strontium Titanate.

Wang Z, Loon A, Subramanian A, Gerhold S, McDermott E, Enterkin JA, Hieckel M, Russell BC, Green RJ, Moewes A, Guo J, Blaha P, Castell MR, Diebold U, Marks LD - Nano Lett. (2016)

Convex-hullconstruction (red) of the surface enthalpies in eV/1 × 1 (y-axis) for different TiO2 excess per 1 ×1 unit cell (x-axis), revTP SSh functional. Errorbars are 0.1 eV/1 × 1 cell. Lines are shown for the 2 × na and 2 × nb families, as well asthe 2-phase coexistence (blue dashes) between the 3 × 1 and 2× 4a structures observed for the samples preparedat higher temperatures.13
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834633&req=5

fig4: Convex-hullconstruction (red) of the surface enthalpies in eV/1 × 1 (y-axis) for different TiO2 excess per 1 ×1 unit cell (x-axis), revTP SSh functional. Errorbars are 0.1 eV/1 × 1 cell. Lines are shown for the 2 × na and 2 × nb families, as well asthe 2-phase coexistence (blue dashes) between the 3 × 1 and 2× 4a structures observed for the samples preparedat higher temperatures.13
Mentions: The DFT convex-hull is shown in Figure 4 with error-barsof 0.1 eV/1 × 1 cell. This is a conventional representation ofthe energetics versus composition, and here the enthalpy versus surfaceexcess of TiO2. The lower envelope describes the singleor two-phase coexistence regimes as a function of surface composition.The 2 × na family occur at lower surface excessof TiO2, consistent with coexistence with n × 1 reconstructions for the high-temperature samples.13 At the high TiO2 coverage (right)of the convex hull both 2 × n families are convergingto a straight line to a nominal 2 × ∞ structure (see Supporting Information CIF file). For a straightline, one expects extensive coexistence of structures due to the entropyof mixing similar to that found for the (111) surface,12 which is consistent with the experimental results.

Bottom Line: Such structures can also be viewed as ultrathin films, epitaxed on a substrate.Whereas SrTiO3 (110) invariably terminates with an overlayer of titania, with increasing density its structure switches from n × 1 to 2 × n.At the same time the coordination of the Ti atoms changes from a network of corner-sharing tetrahedra to a double layer of edge-shared octahedra with bridging units of octahedrally coordinated strontium.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Physics, TU Wien , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria.

ABSTRACT
The surfaces of metal oxides often are reconstructed with a geometry and composition that is considerably different from a simple termination of the bulk. Such structures can also be viewed as ultrathin films, epitaxed on a substrate. Here, the reconstructions of the SrTiO3 (110) surface are studied combining scanning tunneling microscopy (STM), transmission electron diffraction, and X-ray absorption spectroscopy (XAS), and analyzed with density functional theory calculations. Whereas SrTiO3 (110) invariably terminates with an overlayer of titania, with increasing density its structure switches from n × 1 to 2 × n. At the same time the coordination of the Ti atoms changes from a network of corner-sharing tetrahedra to a double layer of edge-shared octahedra with bridging units of octahedrally coordinated strontium. This transition from the n × 1 to 2 × n reconstructions is a transition from a pseudomorphically stabilized tetrahedral network toward an octahedral titania thin film with stress-relief from octahedral strontia units at the surface.

No MeSH data available.


Related in: MedlinePlus