Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Nov 5;11(21):9038-9044.
doi: 10.1021/acs.jpclett.0c02268. Epub 2020 Oct 12.

Structural Characterization of a Novel Two-Dimensional Material: Cobalt Sulfide Sheets on Au(111)

Mahesh K Prabhu  1 , Dajo Boden  1 , Marcel J Rost  2 , Jörg Meyer  1 , Irene M N Groot  1
Affiliations

Structural Characterization of a Novel Two-Dimensional Material: Cobalt Sulfide Sheets on Au(111)

Mahesh K Prabhu et al. J Phys Chem Lett. .

Abstract

Transition metal dichalcogenides (TMDCs) are a type of two-dimensional (2D) material that has been widely investigated by both experimentalists and theoreticians because of their unique properties. In the case of cobalt sulfide, density functional theory (DFT) calculations on free-standing S-Co-S sheets suggest there are no stable 2D cobalt sulfide polymorphs, whereas experimental observations clearly show TMDC-like structures on Au(111). In this study, we resolve this disagreement by using a combination of experimental techniques and DFT calculations, considering the substrate explicitly. We find a 2D CoS(0001)-like sheet on Au(111) that delivers excellent agreement between theory and experiment. Uniquely this sheet exhibits a metallic character, contrary to most TMDCs, and exists due to the stabilizing interactions with the Au(111) substrate.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
2D cobalt sulfide supported on Au(111). (a) Large-scale STM image showing single-layer cobalt sulfide sheets. A modified reconstruction of Au(111) due to H2S exposure with a long-range hexagonal arrangement is seen on the steps of gold. The respective phases are marked. (b) Measured height profile along the blue dashed line marked A in panel a. (c) Atomically resolved STM image of the 2D cobalt sulfide. The rhombus-shaped unit cell is outlined in blue with the two triangular halves demarcated by a green dotted line and enlarged in the inset for the sake of clarity. Image acquired at a sample voltage of −0.7 V. (d) LEED pattern of cobalt sulfide sheets on Au(111) with an incident energy of 95 eV. The diffraction spots of the Au(111) surface are indicated by blue circles. The inset shows a close-up of the Au spot that shows that the spots due to herringbone reconstruction are reduced to spot broadening.
Figure 2
Figure 2
XPS spectra of 2D cobalt sulfide supported on Au(111) after flash annealing to 673 K to remove sulfur species adsorbed on the Au(111) terraces: (a) Co2p and (b) S2p.
Figure 3
Figure 3
Schematic models of 7 × 7 overlayer structures on Au(111) comprised of (a) Co3S4(111)-like and (c) CoS(0001)-like S–Co–S sheets, each with a top (side) view in the top (lower) part of the image. (b and d) Simulated STM images of the structures resulting from relaxation of structures in panels a and c, respectively. Both images were simulated using the Tersoff–Hamann method with a bias potential of −0.3 V. The contrast has been adjusted for better comparison with Figure 1c. The unit cells in panels a–d are colored red.
Figure 4
Figure 4
Positions of the sulfur atoms in the top and bottom basal planes of the cobalt sulfide sheet from Figure 3c. The gold atoms are colored yellow, while the height of the sulfur atoms relative to the lowest atom in each respective layer is indicated in gray scale. The unit cell is displayed as a red rhombus. The height variation in the bottom layer of sulfur atoms due to the lattice mismatch with gold is exaggerated in the top layer. Comparison with Figure 3d indicates the distinct pattern can be explained by height variations of atoms in the top layer, rather than any electronic effect.
Figure 5
Figure 5
Decomposition of the interaction energy for the cobalt sulfide sheet and Au(111) as obtained from DFT calculations. Energies are per S–Co–S unit, with the separated Au(111) slab and free-standing S–Co–S film in equilibrium geometry shown in the leftmost inset defining zero energy. From left to right, the separated Au(111) slab and free-standing S–Co–S film compressed by 1% to coincide with 7/6 Au(111) surface lattice constants, same as before but additionally including the interfacial corrugation of the structure where the S–Co–S film and Au(111) are in contact, which is finally the case in the rightmost relaxed 7 × 7 S–Co–S overlayer structure on Au(111) (i.e., same structure as schematically depicted in Figure 3c).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Jariwala D.; Sangwan V. K.; Lauhon L. J.; Marks T. J.; Hersam M. C. Emerging Device Applications for Semiconducting Two-dimensional Transition Metal Dichalcogenides. ACS Nano 2014, 8, 1102–1120. 10.1021/nn500064s. - DOI - PubMed
    1. Chhowalla M.; Shin H. S.; Eda G.; Li L.-J.; Loh K. P.; Zhang H. The Chemistry of Two-dimensional Layered Transition Metal Dichalcogenide Nanosheets. Nat. Chem. 2013, 5, 263–275. 10.1038/nchem.1589. - DOI - PubMed
    1. Geim A. K.; Grigorieva I. V. Van Der Waals Heterostructures. Nature 2013, 499, 419–425. 10.1038/nature12385. - DOI - PubMed
    1. Lightcap I. V.; Kosel T. H.; Kamat P. V. Anchoring Semiconductor and Metal Nanoparticles on a Two-dimensional Catalyst Material Storing and Shuttling Electrons with Reduced Graphene Oxide. Nano Lett. 2010, 10, 577–583. 10.1021/nl9035109. - DOI - PubMed
    1. Cao X. H.; Yin Z. Y.; Zhang H. Three-dimensional Graphene Materials: Preparation, Structures and Application in Supercapacitors. Energy Environ. Sci. 2014, 7, 1850–1865. 10.1039/C4EE00050A. - DOI
  NODES
twitter 2