Temperature dependence of the dielectric function of monolayer MoS2

Le, Van Long; Kim, T.J.; Park, H.G.; Nguyễn, Hoàng Tùng; Nguyen, Xuan Au; Kim, Y.D.

doi:10.1016/j.cap.2018.10.007

Cited by 18 publications

(7 citation statements)

References 34 publications

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“…However, the intensity of the signal is lower than the experimental one, and the second expected excitonic transition c2-v1 is not visible because of the overlap with the A peak. The present data are also in line with thermal ellipsometry data at 35 K measured by Le et al (2019), who measured A = 2.91 eV and the K-K 0 transition at 1.96 eV.…”

Section: Optical Response Functionsupporting

confidence: 92%

Structural, elastic, electronic, optical and vibrational properties of single-layered, bilayered and bulk molybdenite MoS₂-2H

Ulian

Valdrè

2023

J Appl Cryst

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In recent years, transition metal dichalcogenides have received great attention since they can be prepared as two-dimensional semiconductors, presenting heterodesmic structures incorporating strong in-plane covalent bonds and weak out-of-plane interactions, with an easy cleavage/exfoliation in single or multiple layers. In this context, molybdenite, the mineralogical name of molybdenum disulfide, MoS2, has drawn much attention because of its very promising physical properties for optoelectronic applications, in particular a band gap that can be tailored with the material's thickness, optical absorption in the visible region and strong light–matter interactions due to the planar exciton confinement effect. Despite this wide interest and the numerous experimental and theoretical articles in the literature, these report on just one or two specific features of bulk and layered MoS2 and sometimes provide conflicting results. For these reasons, presented here is a thorough theoretical analysis of the different aspects of bulk, monolayer and bilayer MoS2 within the density functional theory (DFT) framework and with the DFT-D3 correction to account for long-range interactions. The crystal chemistry, stiffness, and electronic, dielectric/optical and phonon properties of single-layered, bilayered and bulk molybdenite have been investigated, to obtain a consistent and detailed set of data and to assess the variations and cross correlation from the bulk to single- and double-layer units. The simulations show the indirect–direct transition of the band gap (K–K′ in the first Brillouin zone) from the bulk to the single-layer structure, which however reverts to an indirect transition when a bilayer is considered. In general, the optical properties are in good agreement with previous experimental measurements using spectroscopic ellipsometry and reflectivity, and with preliminary theoretical simulations.

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Section: Optical Response Functionsupporting

confidence: 92%

Structural, elastic, electronic, optical and vibrational properties of single-layered, bilayered and bulk molybdenite MoS₂-2H

Ulian

Valdrè

2023

J Appl Cryst

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“…These are the excited excitonic states, marked as B 2s and B 3s . These peaks were not observed in previously reported ellipsometric data analysis of single-layer MoS 2 [52][53][54][55][56][57][58][59], but they have been identified in photoluminescence excitation spectroscopy [48]. We have been able to extract the B 2s peak from ellipsometry measurements by numerically Table II and in Table III.…”

Section: Comparison Of Computed and Measured χ And σmentioning

confidence: 70%

Surface susceptibility and conductivity of MoS2 and WSe2 monolayers: A first-principles and ellipsometry characterization

Elliott

Umari

et al. 2020

Phys. Rev. B

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“…The excitonic peak structure of the dielectric functions shown in Figure 5 is similar to that reported in previous works. 37−39,49,57−62 However, the amplitude of the A, B, and C peaks in ε i is much lower than in the case of large-area MoS 2 monolayers 39,58,59,61,63,64 and few layers. [37][38][39]45,57,62 The amplitude of ε i shows a complex behavior with the increasing number of layers, 37,39 and it exhibits a "W" like profile as a consequence of the different weights of decreasing excitonic effects, the increasing joint density of states, and the mass density increase in relatively thick MoS 2 .…”

Section: Resultsmentioning

confidence: 97%

Ellipsometric Investigation of Thick Vertically Oriented MoS₂ Films Grown on Mo Foil at High Temperatures

2021

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Thin films of MoS2 with vertically aligned layers have been less investigated than their horizontal counterparts although they find important applications in energy storage, catalysis, and solar energy harvesting. Many applications require precise control of the film thickness and homogeneity. In this context, spectroscopic ellipsometry is a powerful technique that allows precise determination of the film thickness and evaluation of the film homogeneity and crystallinity from the features of the dielectric function spectrum. Homogeneous films of MoS2 were grown by chemical vapor deposition by sulfurizing Mo foils in sulfur vapor at atmospheric pressure in the 800–1000°C temperature range. The surface topography obtained by scanning electron microscopy images was characterized by vertical structures with a platelet-like morphology. Fractured cross sections showed compact MoS2 films with uniform thickness and a columnar morphology compatible with a vertical orientation of the layers. The vertical alignment was confirmed by Raman spectroscopy which showed an E1 2g to A1g peak ratio of around 0.3. The ellipsometric spectra could be adequately modeled with two-phase (MoS2/air) or three-phase (Mo/MoS2/air) models depending on the MoS2 film thickness. The polycrystalline structure of the MoS2 film was evidenced in the small amplitude of excitonic features in the complex dielectric function. The film thickness rapidly increases with formation temperature at high temperatures. Whereas at 650 °C, the film has a thickness of 40 nm, it increases from 200 to 1000 nm in the 800–1000°C temperature range after a growth time of 10 min.

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Temperature dependence of the dielectric function of monolayer MoS2

Cited by 18 publications

References 34 publications

Structural, elastic, electronic, optical and vibrational properties of single-layered, bilayered and bulk molybdenite MoS₂-2H

Structural, elastic, electronic, optical and vibrational properties of single-layered, bilayered and bulk molybdenite MoS₂-2H

Surface susceptibility and conductivity of MoS2 and WSe2 monolayers: A first-principles and ellipsometry characterization

Ellipsometric Investigation of Thick Vertically Oriented MoS₂ Films Grown on Mo Foil at High Temperatures

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Temperature dependence of the dielectric function of monolayer MoS2

Cited by 18 publications

References 34 publications

Structural, elastic, electronic, optical and vibrational properties of single-layered, bilayered and bulk molybdenite MoS2-2H

Structural, elastic, electronic, optical and vibrational properties of single-layered, bilayered and bulk molybdenite MoS2-2H

Surface susceptibility and conductivity of MoS2 and WSe2 monolayers: A first-principles and ellipsometry characterization

Ellipsometric Investigation of Thick Vertically Oriented MoS2 Films Grown on Mo Foil at High Temperatures

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Product

Resources

About

Structural, elastic, electronic, optical and vibrational properties of single-layered, bilayered and bulk molybdenite MoS₂-2H

Structural, elastic, electronic, optical and vibrational properties of single-layered, bilayered and bulk molybdenite MoS₂-2H

Ellipsometric Investigation of Thick Vertically Oriented MoS₂ Films Grown on Mo Foil at High Temperatures