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Scalable solution-phase epitaxial growth of symmetry-mismatched heterostructures on two-dimensional crystal soft template

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Science Advances  07 Oct 2016:
Vol. 2, no. 10, e1600993
DOI: 10.1126/sciadv.1600993
  • Fig. 1 Schematic illustration for the symmetry-mismatched epitaxial growth of PbSe crystal on Bi2Se3 nanoplate.

    (A) Bi2Se3 nanoplate was first grown in solution. (B) Controlled injection of Pb and Se precursor into the Bi2Se3 nanoplate dispersion initiates the nucleation of PbSe on the nanoplate. (C) Final PbSe/Bi2Se3 heterostructure is produced after the reaction reaches the equilibrium in 3 hours. (D) The deposition of PbSe on Bi2Se3 nanoplate continues as the reaction proceeds.

  • Fig. 2 TEM study of the PbSe/Bi2Se3 heterostructure.

    (A) Top-view TEM analysis of the interface of the PbSe/Bi2Se3 and pristine Bi2Se3 region as indicated by a blue dashed line. Scale bar, 20 nm. (B) HRTEM image of the PbSe/Bi2Se3 region. Scale bar, 5 nm. (C) SAED taken from the area in (B) with the guiding label to feature the symmetry of the diffraction spots. (D) Atomic crystal structure of the (001) plane in PbSe with a blue square to display the symmetry. (E) Atomic crystal structure of the (0001) plane in Bi2Se3 with a red hexagon to display the symmetry (sixfold, instead of threefold, is used to simplify the visualization). (F) Side view of the heterostructure with the relative orientation indicated by the electron diffraction. (G) Electron diffraction pattern of the pristine Bi2Se3 region. Insets are the zoom-in images on two separate diffraction spots. (H) Electron diffraction pattern of the PbSe/Bi2Se3 region. Insets are the zoom-in images on two separate diffraction spots, both showing a doublet split. (I) Simulated moiré pattern based on a pristine Bi2Se3 and expanded Bi2Se3 (0001) plane that exhibits the same symmetry and periodicity as those observed in (A) and (B). Scale bar, 5 nm.

  • Fig. 3 Electron diffraction and moiré pattern analysis of the PbSe/Bi2Se3 heterostructure.

    (A) Cross-sectional TEM image of the PbSe/Bi2Se3 heterostructure prepared by focused ion beam (FIB). A polycrystalline Pt layer was deposited on top of the nanoplate for sample preparation. Scale bar, 5 nm. (B) Cross-sectional high-angle annular dark-field STEM (HAADF-STEM) image of the PbSe/Bi2Se3 heterostructure. Scale bar, 10 nm. (C) Composition line scan profile across the interface [along the dashed red line in (B)] obtained by the energy-dispersive x-ray spectroscopy integrated with HAADF-STEM (HAADF-STEM-EDS), with normalized intensity. a.u., arbitrary units. (D) Elemental mapping of Pb, Bi, and Se in the region indicated by the red square in (B). (E) Cross-sectional HRTEM analysis of the interface. Scale bar, 1 nm. (F) Schematic illustration on the atomic structure of the PbSe/Bi2Se3 corresponding to the perspective in (E).

  • Fig. 4 DFT calculation of heterostructure models with various orientations.

    (A to C) Atomic structure with Bi2Se3 (0001) parallel to PbSe (001) (A), (011) (B), and (111) (C) after energy relaxation. Table shows the interfacial energy, bond length, and dangling bond density for each type of interface.

  • Fig. 5 Thermoelectric performance of pristine Bi2Se3 nanoplate and the heterostructure.

    (A to F) The electrical conductivity σ (A), Seebeck coefficient S (B), power factor σS2 (C), thermal diffusivity α (D), thermal conductivity κ (E), and figure of merit ZT (F) of pristine Bi2Se3 nanoplate and PbSe/Bi2Se3 heterostructure bulk, which were prepared by hot pressing under the same conditions.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/10/e1600993/DC1

    fig. S1. PXRD pattern for the PbSe/Bi2Se3 heterostructure.

    fig. S2. HRTEM analysis of the pure Bi2Se3 region in the PbSe/Bi2Se3 heterostructure.

    fig. S3. Low-magnification representative STEM image of the PbSe/Bi2Se3 heterostructure.

    fig. S4. High-magnification representative STEM image of the PbSe/Bi2Se3 heterostructure.

    fig. S5. Atomic crystal structure for the intrinsic and expanded Bi2Se3 (0001) layers.

    note S1. DFT modeling of PbSe (001)–Bi2Se3 (001), PbSe (011)–Bi2Se3 (0001), and PbSe (111)–Bi2Se3 (0001) interfaces.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. PXRD pattern for the PbSe/Bi2Se3 heterostructure.
    • fig. S2. HRTEM analysis of the pure Bi2Se3 region in the PbSe/Bi2Se3 heterostructure.
    • fig. S3. Low-magnification representative STEM image of the PbSe/Bi2Se3 heterostructure.
    • fig. S4. High-magnification representative STEM image of the PbSe/Bi2Se3 heterostructure.
    • fig. S5. Atomic crystal structure for the intrinsic and expanded Bi2Se3 (0001) layers.
    • note S1. DFT modeling of PbSe (001)–Bi2Se3 (001), PbSe (011)–Bi2Se3 (0001), and PbSe (111)–Bi2Se3 (0001) interfaces.

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