Spatial variation of geometry, binding, and electronic properties in the moiré superstructure of MoS₂ on Au(111)

Abstract

The lattice mismatch between a monolayer of MoS2 and its Au(111) substrate induces a moiré superstructure. The local variation of the registry between sulfur and gold atoms at the interface leads to a periodic pattern of strongly and weakly interacting regions. In consequence, also the electronic bands show a spatial variation. We use scanning tunneling microscopy and spectroscopy (STM/STS), x-ray photoelectron spectroscopy (XPS) and x-ray standing wave (XSW) for a determination of the geometric and electronic structure. The experimental results are corroborated by density functional theory (DFT). We obtain the geometric structure of the supercell with high precision, identify the fraction of interfacial atoms that are strongly interacting with the substrate, and analyze the variation of the electronic structure in dependence of the location within the moiré unit cell and the nature of the band.

Band Alignments, Electronic Structure, and Core-Level Spectra of Bulk Molybdenum Dichalcogenides (MoS2, MoSe2, and MoTe2)

“…This weak component is not thought to be due to residual surface contamination as its relative intensity is stronger in the HAXPES measurement and the chemical shift is smaller than typically reported for contaminant peaks. A component at ∼0.3 eV higher binding energy than the main S 2p line has been observed previously for monolayer MoS 2 , where it was associated with some of the subsurface sulfur, close to the Au substrate. , Clearly, the same interpretation cannot be made here as our data is from in situ cleaved bulk MoS 2 . We therefore tentatively associate the component with some kind of structural defect, possibly generated by cleaving.…”

“…A component at ∼0.3 eV higher binding energy than the main S 2p line has been observed previously for monolayer MoS 2 , where it was associated with some of the subsurface sulfur, close to the Au substrate. 90,91 Clearly, the same interpretation cannot be made here as our data is from in situ cleaved bulk MoS 2 . We therefore tentatively associate the component with some kind of structural defect, possibly generated by cleaving.…”

Elastic properties of moiré lattices in epitaxial two-dimensional materials

“…Mechanical instability. -Our calculations predict Λ values larger by ∼1 Å and ∼2 Å, respectively, than experimental values for graphene/Ir [31,32] and MoS 2 /Au [37,38] (Table I). Such discrepancies are expected as a result of the heteroepitaxial stress building up as the samples are cooled down after growth, due to the mismatch in thermal expansion coefficients of the 2D material and the substrate.…”

“…-High-resolution measurement of Λ, ∆ and d is notoriously challenging experimentally. Graphene on Ir(111) is one of the few systems for which this has been done [21,25,[31][32][33][34], and MoS 2 /Au(111) another one, albeit to a lesser extent [36][37][38]. The measured structural parameters are reported in Table I -∆ estimates vary with the tunneling imaging conditions for graphene/Ir [33], even more so for MoS 2 /Au [37].…”

“…S6(b,c) of the Supplemental Material [39]]. The [37,38] 0.37 [37] topography is essentially inherited from the C-Ir interaction ( and Table I) and graphene/Ir(111) is a weakly nanorippled system storing little elastic energy. This holds too for graphene slightly twisted (fractions of degrees are often observed experimentally [33,45]) with respect to Ir(111) (Sec.…”