Single layer MoS${}_{2}$ on the Cu(111) surface: First-principles electronic structure calculations

Single layer MoS $_{2}$ on the Cu(111) surface: First-principles electronic structure calculations

Duy Le, Dezheng Sun, Wenhao Lu, Ludwig Bartels, and Talat S. Rahman

Phys. Rev. B 85, 075429 – Published 23 February 2012

Abstract

First-principles calculations of the geometric and electronic structures of a single layer of molybdenum disulfide (MoS $_{2}$ ) on Cu(111) utilizing the van der Waals density functional show three energetically equivalent stacking types and a Moiré pattern whose periodicity is in agreement with experimental findings. The layer is found not to be purely physisorbed on the surface, rather there exists a chemical interaction between it and the Cu surface atoms. We also find that the MoS $_{2}$ film is not appreciably buckled, while the top Cu layer gets reorganized and vertically disordered. The sizes of Moiré patterns for a single layer of MoS $_{2}$ adsorbed on other close-packed metal surfaces are also estimated by minimizing the lattice mismatch between the film and the substrate.

Received 14 October 2011

DOI:https://doi.org/10.1103/PhysRevB.85.075429

Authors & Affiliations

Duy Le¹, Dezheng Sun², Wenhao Lu², Ludwig Bartels², and Talat S. Rahman^1,*

¹Department of Physics, University of Central Florida, Orlando, Florida 32816, USA
²Pierce Hall, University of California Riverside, Riverside, California 92521, USA

^*Talat.Rahman@ucf.edu

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Vol. 85, Iss. 7 — 15 February 2012

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Images

Figure 1
Atomic model of a single layer MoS $_{2}$ in $α$ (a), $β$ (b), and $γ$ (c) stacking on Cu(111). Yellow (gray), blue (dark), and white circles represent S, Mo, Cu surface atoms, respectively. The dark and light gray spaces between Cu surface atoms are, respectively, fcc and hcp sites of the Cu(111) surface. Rings numbered from R1 to R5 highlight the equivalent S atoms. Triangles highlight groups of three equivalent S atoms. Dashed lines indicate the direction of the shifts between stacking types.Reuse & Permissions
Figure 2
(a) and (b) $19 \times 19$ Å $^{2}$ simulated STM image (Ref. 23) of $α$ and $β$ stacking. The color scale goes from dark to bright corresponding to the height from 0 to 0.34 Å. Bias voltage is $- 0.560$ V and iso LDOS value is $10^{- 6}$ Ry $^{- 1}$ . A $7 \times 7 \times 1$ mesh is used to sample the Brillouin zone. Up- and down-pointing triangles highlight the three spots with the same contrast and corresponding to those in Fig. 1. Parallelograms indicate the Moiré unit cells. (c) STM image of two adjacent MoS $_{2}$ islands for comparing the difference in appearance of the Moiré pattern to panels (a) and (b). The parallelogram indicates the Moiré unit cell. The image size is $11.5$ nm $\times$ $10.5$ nm, the bias is $- 0.475$ V, and the tunneling current is 110 pA.Reuse & Permissions
Figure 3
Intralayer buckling along the long diagonal of Moiré unit cells of $α$ (a), $β$ (b), and $γ$ (c) stacking. Circles represent S, Mo, and Cu atoms. $B$ -spline fits (solid lines) are included for eye guidance purpose. Vertical lines point out relative positions of the rings R1, R2, R4, and R5. The numbers (in Å) in the left and right are the average interlayer distances and the buckling of layers.Reuse & Permissions
Figure 4
(a) Valence charge density along the vertical plane passing through the long diagonal of the Moiré unit cell of the $α$ stacking of MoS $_{2}$ on Cu(111). R1, R2, R4, and R5 indicate the rings [see Fig, 1a] to which S atoms belong. The labels (S, Mo, Cu) on the left map the rows of S, Mo, and Cu, respectively. Contour values are 0.02, 0.03, 0.04, 0.05, and 0.09 au. The 0.03 contour is highlighted (the thickest line) for guidance the eyes. (b) Density of redistribution of charge in the region limited by a broken rectangular in panel (a). Yellowish (bright) and blueish (dark) regions indicate, respectively, accumulation and depletion of charge. The gray background corresponds to zero redistribution. The scale going from blue (dark) to yellow (bright) corresponds to the variation from $- 7.5 \times 10^{- 3}$ to $7.5 \times 10^{- 3}$ a.u.Reuse & Permissions

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