Research ArticleMATERIALS SCIENCE

Borophene-graphene heterostructures

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Science Advances  11 Oct 2019:
Vol. 5, no. 10, eaax6444
DOI: 10.1126/sciadv.aax6444
  • Fig. 1 Graphene and borophene-graphene heterostructures on Ag(111).

    (A) STM topography image of as-grown single-layer graphene on Ag(111) (Vs = 0.3 V, It = 500 pA) and (B) the corresponding differential tunneling conductance map. (C) Differential tunneling conductance curves measured on Ag(111) and graphene (Gr/Ag) with a stabilization condition of Vs = −0.5 V and It = 200 pA . (D) Atomically resolved STM topography image of as-grown graphene (Vs = 10 mV, It = 2 nA). (E) STM topography image of lateral and vertical heterostructures between borophene and graphene. Linear features in three directions are indicated by the yellow arrows in the region of borophene-intercalated graphene (Gr/B) (Vs = −5 mV, It = 530 pA). a.u., arbitrary units.

  • Fig. 2 Substitutional boron doping of graphene.

    (A) STM topography image of single-layer graphene on Ag with a bare metal tip after boron deposition and (B) the simultaneously acquired |dlnI/dz| image (Vs = −4 mV, It = 660 pA). The white dashed circles show an example where the |dlnI/dz| map offers improved spatial resolution. (C) Geometric imaging of the same region as in (A) and (B) with a CO-functionalized tip in CH mode (stabilized at Vs = −11 mV, It = 80 pA), revealing dopants pointing in opposite directions (red and yellow triangles). (D) Substitutional boron dopants in the two sublattices of graphene (stabilized at Vs = −11 mV, It = 100 pA). (E) Geometric imaging of a v1/5 borophene sheet with a CO-functionalized tip in CH mode (stabilized at Vs = −8 mV, It = 500 pA).

  • Fig. 3 Borophene-graphene lateral heterostructures.

    (A) Geometric imaging of the borophene-graphene lateral heterointerface with a CO-functionalized tip in CH mode, which resolves both lattices simultaneously (stabilized at Vs = −10 mV, It = 350 pA). The boron row direction is aligned with the graphene ZZ direction as indicated by the black and white double arrows, respectively. (B) Zoomed-in image of the heterointerface with a ZZ graphene termination marked by the yellow dashed line in (A) with an overlaid lattice schematic (stabilized at Vs = −10 mV, It = 350 pA). (C) Series of STS spectra taken across a lateral heterointerface between borophene and graphene along the red dashed line in the inset with a stabilization condition of Vs = −0.2 V, It = 100 pA. Inset: Stabilized at Vs = −10 mV, It = 350 pA. (D) Differential tunneling conductance map (logarithmic scale) of a borophene-graphene lateral heterointerface at Vs = 0.6 V (stabilized at Vs = −0.2 V, It = 40 pA). (E) Three series of STS spectra taken across three heterointerfaces along the white dashed lines in (D) (stabilized at Vs = −0.2 V, It = 40 pA).

  • Fig. 4 Borophene-graphene vertical heterostructures.

    (A) STM topography image of a triangular borophene-intercalated graphene domain (Vs = 35 mV, It = 250 pA) with a CO-functionalized tip in CC mode and (B) differential tunneling conductance map of the same region (Vs = −50 mV, It = 200 pA). (C) Point STS spectra of graphene and borophene-intercalated graphene (stabilized at Vs = −0.1 V, It = 100 pA). (D) Zoomed-in STM image of the graphene-graphene/borophene interface (red arrowheads) indicated by the red dashed rectangle in (A) (Vs = 35 mV, It = 250 pA). (E) Zoomed-in STM image of borophene-intercalated graphene domain indicated by the yellow dashed rectangle in (A) with a CO-functionalized tip in CH mode (stabilized at Vs = 30 mV, It = 500 pA). (F) STM topography image and (G) simultaneously acquired |dlnI/dz| image of borophene-intercalated graphene with a bare metal tip (Vs = −8 mV, It = 500 pA). A linear structure with 5 Å periodicity is marked in (F). The graphene lattice is marked in (G). (H) Fourier transform of the image in (G), showing an orthogonal pair of points corresponding to a rectangular lattice (3 Å × 5 Å). (I) Schematic representation of the rotationally commensurate borophene-graphene vertical heterostructure, where the boron row direction and the graphene AC direction are aligned as indicated by the pink and gray arrows, respectively.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/10/eaax6444/DC1

    Supplementary Text

    Fig. S1. |dlnI/dz| measurements.

    Fig. S2. Low-temperature graphene growth.

    Fig. S3. Multiple rotational lattice alignments between graphene and Ag(111).

    Fig. S4. Comparison of different imaging channels with CO-functionalized tips.

    Fig. S5. Random distribution of boron dopants in two sublattices of graphene.

    Fig. S6. The absence of hidden Kekulé order.

    Fig. S7. Increased spatial resolution enabled by CO functionalization.

    Fig. S8. Resolving the geometric structures of borophene and graphene simultaneously.

    Fig. S9. Atomically resolved borophene-graphene heterointerfaces with ZZ graphene terminations.

    Fig. S10. Atomically resolved borophene-graphene heterointerfaces with AC graphene terminations.

    Fig. S11. Electronic transitions across various graphene-borophene heterointerfaces.

    Fig. S12. Electronic transitions across graphene-Ag and borophene-Ag interfaces.

    Fig. S13. Comparing images taken with bare and CO-functionalized tips.

    Fig. S14. Comparing borophene-intercalated graphene with a v1/6 borophene sheet.

    Fig. S15. Control of heterostructures and distribution of intercalated graphene domains.

    References (3136)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • Fig. S1. |dlnI/dz| measurements.
    • Fig. S2. Low-temperature graphene growth.
    • Fig. S3. Multiple rotational lattice alignments between graphene and Ag(111).
    • Fig. S4. Comparison of different imaging channels with CO-functionalized tips.
    • Fig. S5. Random distribution of boron dopants in two sublattices of graphene.
    • Fig. S6. The absence of hidden Kekulé order.
    • Fig. S7. Increased spatial resolution enabled by CO functionalization.
    • Fig. S8. Resolving the geometric structures of borophene and graphene simultaneously.
    • Fig. S9. Atomically resolved borophene-graphene heterointerfaces with ZZ graphene terminations.
    • Fig. S10. Atomically resolved borophene-graphene heterointerfaces with AC graphene terminations.
    • Fig. S11. Electronic transitions across various graphene-borophene heterointerfaces.
    • Fig. S12. Electronic transitions across graphene-Ag and borophene-Ag interfaces.
    • Fig. S13. Comparing images taken with bare and CO-functionalized tips.
    • Fig. S14. Comparing borophene-intercalated graphene with a v1/6 borophene sheet.
    • Fig. S15. Control of heterostructures and distribution of intercalated graphene domains.
    • References (3136)

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