<i>In situ</i> exfoliated 2D molybdenum disulfide analyzed by XPS

Wang, Xinglu; Cormier, Christopher R.; Khosravi, Ava; Smyth, Christopher M.; Shallenberger, Jeffrey R.; Addou, Rafik; Wallace, Robert M.

doi:10.1116/6.0000153

Cited by 22 publications

(14 citation statements)

References 10 publications

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“…The principal one represents 70–80% of the total signal. The right ones (see the yellow doublets in Figure 2 b,c) are located at energy values that are comparable with the ones previously reported for molybdenum disulfide (S 2p 3/2 at 162.0 eV; Mo 3d 5/2 at 229.6 eV) [ 61 ]. The second components on the left of the principal ones (the blue doublets in Figure 2 b,c) can be attributed to local defects in the molybdenum disulfide lattice due to the presence of oxygen atoms.…”

Section: Resultssupporting

confidence: 87%

Electrodeposition of Molybdenum Disulfide (MoS2) Nanoparticles on Monocrystalline Silicon

et al. 2022

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Molybdenum disulfide (MoS2) has attracted great attention for its unique chemical and physical properties. The applications of this transition metal dichalcogenide (TMDC) range from supercapacitors to dye-sensitized solar cells, Li-ion batteries and catalysis. This work opens new routes toward the use of electrodeposition as an easy, scalable and cost-effective technique to perform the coupling of Si with molybdenum disulfide. MoS2 deposits were obtained on n-Si (100) electrodes by electrochemical deposition protocols working at room temperature and pressure, as opposed to the traditional vacuum-based techniques. The samples were characterized by X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Rutherford Back Scattering (RBS).

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Section: Resultssupporting

confidence: 87%

Electrodeposition of Molybdenum Disulfide (MoS2) Nanoparticles on Monocrystalline Silicon

et al. 2022

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“…The resulting S/Mo atomic concentration (AC) ratios are found to be 1.80, 1.84, and 1.88, respectively, and these values are smaller than the MoS 2 value. There is an excellent agreement between our AES results and the recently reported result of quantitative X-ray photoelectron spectroscopy (XPS) analysis for the exfoliated (0001) MoS 2 surface after annealing under ultrahigh vacuum (UHV) conditions [31]. In this case, a sulfur-deficient surface composition of MoS 1.8 was found.…”

Section: Auger Electron Spectroscopy (Aes) Characterizationsupporting

confidence: 89%

Surface Characterization of MoS2 Atomic Layers Mechanically Exfoliated on a Si Substrate

et al. 2020

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Mo disulfide overlayers with the thickness exceeding 1.77 nm were obtained on Si substrates through mechanical exfoliation. The resulting Mo disulfide flakes were then analyzed ex situ using combination of Auger electron spectroscopy (AES), elastic-peak electron spectroscopy (EPES) and scanning electron microscopy (SEM) in order to characterize their surface chemical composition, electron transport phenomena and surface morphology. Prior to EPES measurements, the Mo disulfide surface was sputter-cleaned and amorphized by 3 kV argon ions, and the resulting S/Mo atomic ratio varied in the range 1.80–1.88, as found from AES measurements. The SEM images revealed single crystalline small-area (up to 15 μm in lateral size) Mo disulfide flakes having polygonal or near-triangular shapes. Such irregular-edged flakes exhibited high crystal quality and thickness uniformity. The inelastic mean free path (IMFP), characterizing electron transport, was evaluated from the relative EPES using Au reference material for electron energies E = 0.5–2 keV. Experimental IMFPs, λ, determined for the AES-measured surface compositions were approximated by the simple function λ = kEp, where k = 0.0289 and p = 0.946 were fitted parameters. Additionally, these IMFPs were compared with IMFPs resulting from the two methods: (i) present calculations based on the formalism of the Oswald et al. model; (ii) the predictive equation of Tanuma et al. (TPP-2M) for the measured Mo0.293S0.551C0.156 surface composition (S/Mo = 1.88), and also for stoichiometric MoS2 composition. The fitted function was found to be reasonably consistent with the measured, calculated and predicted IMFPs. We concluded that the measured IMFP value at 0.5 keV was only slightly affected by residual carbon contamination at the Mo disulfide surface.

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“…One may easily overlook the appearance of Ni/MoS x states due to the low intensities of these states after Ni deposition under UHV conditions, however, after careful fitting and deconvolution using reference samples . The detection of reaction products shown in Figure a can be deduced.…”

Section: Resultsmentioning

confidence: 99%

Interface Chemistry and Band Alignment Study of Ni and Ag Contacts on MoS₂

Wang

Kim

Wallace

2021

ACS Appl. Mater. Interfaces

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High contact resistance of transition-metal dichalcogenide (TMD)-based devices is one of the bottlenecks that limit the application of TMDs in various domains. Contact resistance of TMD-based devices is strongly related to the interface chemistry and band alignment at the contact metal/TMD interfaces. To understand the metal/MoS 2 interface chemistry and band alignment, Ni and Ag metal contacts are deposited on MoS 2 bulk and chemical vapor deposition bilayer MoS 2 (2L-MoS 2 ) film samples under ultrahigh vacuum (∼3 × 10 −11 mbar) and high vacuum (∼3 × 10 −6 mbar) conditions. X-ray photoelectron spectroscopy is used to characterize the interface chemistry and band alignment of the metal/MoS 2 stacks. Ni forms covalent contact on MoS 2 bulk and 2L-MoS 2 film by reducing MoS 2 to form interfacial metal sulfides. In contrast, van der Waals gaps form at the Ag/MoS 2 bulk and Ag/ 2L-MoS 2 film interfaces, proved by the absence of an additional metal sulfide chemical state and the detection of Ag islands on the surface. Different from other metal/MoS 2 systems studied in this work, Ag shows potential to form an Ohmic contact on MoS 2 bulk regardless of the deposition ambient. Fermi levels (E F 's) are pinned near the intrinsic E F of the 2L-MoS 2 film with high defect density regardless of the work function of the metal, which highlights the impact of substrate defect density on the E F pinning effect and contact resistance.

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In situ exfoliated 2D molybdenum disulfide analyzed by XPS

Cited by 22 publications

References 10 publications

Electrodeposition of Molybdenum Disulfide (MoS2) Nanoparticles on Monocrystalline Silicon

Electrodeposition of Molybdenum Disulfide (MoS2) Nanoparticles on Monocrystalline Silicon

Surface Characterization of MoS2 Atomic Layers Mechanically Exfoliated on a Si Substrate

Interface Chemistry and Band Alignment Study of Ni and Ag Contacts on MoS₂

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In situ exfoliated 2D molybdenum disulfide analyzed by XPS

Cited by 22 publications

References 10 publications

Electrodeposition of Molybdenum Disulfide (MoS2) Nanoparticles on Monocrystalline Silicon

Electrodeposition of Molybdenum Disulfide (MoS2) Nanoparticles on Monocrystalline Silicon

Surface Characterization of MoS2 Atomic Layers Mechanically Exfoliated on a Si Substrate

Interface Chemistry and Band Alignment Study of Ni and Ag Contacts on MoS2

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Interface Chemistry and Band Alignment Study of Ni and Ag Contacts on MoS₂