Research ArticleSEMICONDUCTORS

Van der Waals metal-semiconductor junction: Weak Fermi level pinning enables effective tuning of Schottky barrier

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Science Advances  22 Apr 2016:
Vol. 2, no. 4, e1600069
DOI: 10.1126/sciadv.1600069
  • Fig. 1 Weak FLP at the vdW MSJ.

    (A) Electronic band structure and DOS of a typical vdW MSJ. T-MoS2H-MoS2 is used here as an example, where T-MoS2 is a metal and H-MoS2 is a semiconductor (SC). FL is set to zero. The VBM and CBM of the SC are marked by blue and red dots, respectively. The purple line shows the DOS projected on the semiconductor. Isosurfaces show the spatial distributions of the states. (B) SB heights (Φe for electrons and Φh for holes) between H-MoS2 and various 2D metals. The diagonal line shows the values predicted by the Schottky-Mott model. (C) Charge density change (averaged in the plane parallel to the interface) after the formation of the H-VS2H-MoS2 MSJ. Atom positions perpendicular to the basal plane are shown as distances relative to the center of the interface and marked by horizontal lines. a.u., arbitrary units.

  • Fig. 2 Band alignment between 2D metals and semiconductors.

    Left columns show the electron affinity and ionization potential of semiconductors. Right bars show the work function of metals. The phase is labeled in italics. C stands for pristine graphene, C20N is the N-doped graphene with the C/N ratio of 20:1, and similarly for C20B. For comparison, the work functions of some commonly used 3D metals are also shown.

  • Fig. 3 Origin of work function variation in 2D metals.

    (A) DOS of metallic MX2 (T-MoS2 is used here as an example). FL is set to zero. The black line shows the total DOS, and the other lines are the projected DOS on the orbitals of M and X. (B) Charge density distribution of the states in the electron volt range (−0.025, 0.025) (top and side views). (C) Schematic of coupling between M d states and X p states.

  • Fig. 4 SB heights for H-NbS2 and C20N metals, with various 2D semiconductors.

    C20N with tellurides are not calculated because of the extremely large supercell required for modeling to reduce the lattice mismatch. The red bars indicate the CBM, the blue bars represent the VBM that are set to zero, and the black dots denote the position of FL in the corresponding MSJ.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/4/e1600069/DC1

    fig. S1. Supercell used for modeling the graphene–H-MoS2 junction.

    fig. S2. Comparison of pinning factor between vdW and chemically bonded junctions.

    fig. S3. Φ between 2D H-MoS2 and various 2D metals calculated by using the PBE-D3 method.

    fig. S4. Band structure of H-NbS2H-WSe2 and C20N–H-MoS2 junctions.

    table S1. Comparison of Φ between the PBE and the PBE-D3 methods.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Supercell used for modeling the graphene–H-MoS2 junction.
    • fig. S2. Comparison of pinning factor between vdW and chemically bonded junctions.
    • fig. S3. Φ between 2D H-MoS2 and various 2D metals calculated by using the PBE-D3 method.
    • fig. S4. Band structure of H-NbS2H-WSe2 and C20N–H-MoS2 junctions.
    • table S1. Comparison of Φ between the PBE and the PBE-D3 methods.

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