Investigation of the optical properties of MoS<sub>2</sub> thin films using spectroscopic ellipsometry

Yim, Chanyoung; O’Brien, Maria; McEvoy, Niall; Winters, Sinéad; Mirza, Inam; Lunney, J. G.; Duesberg, Georg S.

doi:10.1063/1.4868108

Cited by 261 publications

(229 citation statements)

References 27 publications

(30 reference statements)

Supporting

Mentioning

207

Contrasting

Unclassified

Order By: Relevance

“…Our extinction coefficient at 3 eV is ß3.4 (see Fig. S3 [38]), which is comparable with that (ß3.2) of Yim et al [32] for ultrathin CVD MoS 2 , but much lower than that (ß5.1) of Shen et al [24]. The higher coefficient could be a result of sample structural quality or the way it was extracted from their four-phase ellipsometric model, even though it contains all similar absorption peaks [24].…”

Section: Resultssupporting

confidence: 78%

“…Recently, SE has also been used to determine the dielectric function of CVD-grown MoS 2 [28,29]. Yim et al [32] have found that, in their four-phase ellipsometric model, the refraction index (n) and the extinction coefficient (k) of their CVD MoS 2 exhibit a dependence on the MoS 2 film thickness. Shen et al [24], using terahertz (THz) absorption and SE, investigated the charge dynamics to show the semiconductor behavior and a blueshift of ß0.2 eV of charge transfer bands compared with those of the bulk material and also determine the dielectric function from 0.73 to 6.42 eV.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Broadband optical properties of large-area monolayer CVD molybdenum disulfide

et al. 2014

View full text Add to dashboard Cite

Recently emerging large-area single-layer MoS 2 grown by chemical vapor deposition has triggered great interest due to its exciting potential for applications in advanced electronic and optoelectronic devices. Unlike gapless graphene, MoS 2 has an intrinsic band gap in the visible which crosses over from an indirect to a direct gap when reduced to a single atomic layer. In this paper, we report a comprehensive study of fundamental optical properties of MoS 2 revealed by optical spectroscopy of Raman, photoluminescence, and vacuum ultraviolet spectroscopic ellipsometry. A band gap of 1.42 eV is determined by the absorption threshold of bulk MoS 2 that shifts to 1.83 eV in monolayer MoS 2 . We extracted the high precision dielectric function up to 9.0 eV, which leads to the identification of many unique interband transitions at high symmetry points in the MoS 2 momentum space. The positions of the so-called A and B excitons in single layers are found to shift upwards in energy compared with those of the bulk form and have smaller separation because of the decreased interactions between the layers. A very strong optical critical point predicted to correspond to a quasiparticle gap is observed at 2.86 eV, which is attributed to optical transitions along the parallel bands between the M and points in the reduced Brillouin zone. The absence of the bulk MoS 2 spin-orbit interaction peak at ß3.0 eV in monolayer MoS 2 is, as predicted, the consequence of the coalescence of nearby excitons. A higher energy optical transition at 3.98 eV, commonly occurring in bulk semiconductors, is associated with a combination of several critical points. Additionally, extending into the vacuum ultraviolet energy spectrum are a series of newly observed oscillations representing optical transitions from valence bands to higher conduction bands of the monolayer MoS 2 complex band structure. These optical transitions herein reported enhance our understanding of monolayer MoS 2 as well as of two-dimensional systems in general and thus provide informative guidelines for MoS 2 optical device designs and theoretical considerations.

show abstract

Section: Resultssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Broadband optical properties of large-area monolayer CVD molybdenum disulfide

et al. 2014

View full text Add to dashboard Cite

show abstract

“…4c) likely arises from dielectric environment differences between bulk and single layer specimens. The extinction coefficient, k, in the region 3 to 4.5 eV is about ∼2.5…3.5, which is comparable with that (∼3.2) of Yim et al [14] for ultrathin CVD MoS 2 and with the data of Li et al [15] for TMDs, but much lower than that (∼5.1) of Shen et al [39]. The higher coefficient, k, could be a result of sample structural quality or the way it was extracted from their four-phase ellipsometric model [39].…”

Section: Resultssupporting

confidence: 76%

“…For optoelectronic device applications of TMDs monolayers to be fully understand, it is also necessary to know the complex refractive index and then to determine optical conductivity. Recently, we have employed the SE to investigate the optical constants of graphene [12,13], however, up to date, SE characterisation of 2D layered TMDs has rarely been reported [14][15][16]. Moreover, additional UV-visible-near-infrared absorption measurements can promote deepening the understanding of the optical response of 2D systems for successful nanooptical device engineering.…”

Section: Introductionmentioning

confidence: 99%

Ellipsometry and optical spectroscopy of low-dimensional family TMDs

Kravets¹

2017

Semicond. Phys. Quantum Electron. Optoelectron.

View full text Add to dashboard Cite

Abstract. Here, we report a comprehensive study of fundamental optical properties of two-dimensional materials. These properties have been ascertained using spectroscopic ellipsometry, optical spectroscopy of Raman scattering, and photoluminescence. We have focused on optical properties of the chemically exfoliated layered TMDs: MoS 2 , MoSe 2 , WS 2 , and WSe 2 . The complex refractive index and optical conductivity within the region 1 to 4.5 eV were extracted, which lead to identification of many unique interband transitions at high symmetry points in the electron band structure. The positions of the so-called A and B excitons in monolayers are found to shift upwards in energy as compared with those of the bulk form and have smaller separation because of the decreased interactions between the layers. For monolayer TMDs, the valence-band spin-orbit splitting at the K point was estimated from the energy difference between the A and B exciton peaks. Our findings of the spin-orbit coupling of ∼0.16, ∼0.26, ∼0.37, and ∼0.55 eV in monolayers MoS 2 , MoSe 2 , WS 2 , and WSe 2 , respectively. All these findings not only extend our understanding the novel electronic structures of mono-and few-layers TMDs but also provide foundation for future technological applications of optoelectronic and spintronic device components.

show abstract

“…For this reason, detailed knowledge of the complex dielectric functions in dependence of the number of layers is highly desirable. Typical methods to extract the dielectric function are ellipsometry measurements under a certain angle of incidence to probe in-plane and out-of-plane components of the light matter interaction done with macroscopically large light spots [122][123][124] . The fabrication of flakes with a precise control over the number [48] .…”

Section: Complex Dielectric Function and Absorbance Of Tmdsmentioning

confidence: 99%

Light–matter interaction in transition metal dichalcogenides and their heterostructures

Wurstbauer¹,

Miller²,

Parzinger³

et al. 2017

J. Phys. D: Appl. Phys.

102

View full text Add to dashboard Cite

Abstract:The investigation of two-dimensional van der Waals materials is a vibrant, fast moving and still growing interdisciplinary area of research. Two-dimensional van der Waals materials are truly two-dimensional crystals with strong covalent in-plane bonds and weak van der Waals interaction between the layers with a variety of different electronic, optical and mechanical properties. A very prominent class of twodimensional materials are transition metal dichalcogenides and amongst them particularly the semiconducting subclass. Their properties include bandgaps in the near-infrared to the visible range, decent charge carrier mobility together with high (photo-)catalytic and mechanical stability and exotic many body phenomena. These characteristics make the materials highly attractive for both fundamental research as well as innovative device applications. Furthermore, the materials exhibit a strong light matter interaction providing a high sun light absorbance of up to 15% in the monolayer limit, strong scattering cross section in Raman experiments and access to excitonic phenomena in van der Waals heterostructures. This review focuses on the light matter interaction in MoS2, WS2, MoSe2, and WSe2 that is dictated by the materials complex dielectric functions and on the multiplicity of studying the first order phonon modes by Raman spectroscopy to gain access to several material properties such as doping, strain, defects and temperature. Two-dimensional materials provide an interesting platform to stack them into van der Waals heterostructures without the limitation of lattice mismatch resulting in novel devices for application but also to study exotic many body interaction phenomena such as interlayer excitons. Future perspectives of semiconducting transition metal dichalcogenides and their heterostructures for applications in optoelectronic devices will be examined and routes to study emergent fundamental problems and manybody quantum phenomena under excitations with photons will be discussed.

show abstract

Investigation of the optical properties of MoS₂ thin films using spectroscopic ellipsometry

Abstract: Articles you may be interested inEffect of metal-ion doping on the optical properties of nanocrystalline ZnO thin films

Cited by 261 publications

References 27 publications

Broadband optical properties of large-area monolayer CVD molybdenum disulfide

Broadband optical properties of large-area monolayer CVD molybdenum disulfide

Ellipsometry and optical spectroscopy of low-dimensional family TMDs

Light–matter interaction in transition metal dichalcogenides and their heterostructures

Contact Info

Product

Resources

About

Investigation of the optical properties of MoS2 thin films using spectroscopic ellipsometry

Abstract: Articles you may be interested inEffect of metal-ion doping on the optical properties of nanocrystalline ZnO thin films

Cited by 261 publications

References 27 publications

Broadband optical properties of large-area monolayer CVD molybdenum disulfide

Broadband optical properties of large-area monolayer CVD molybdenum disulfide

Ellipsometry and optical spectroscopy of low-dimensional family TMDs

Light–matter interaction in transition metal dichalcogenides and their heterostructures

Contact Info

Product

Resources

About

Investigation of the optical properties of MoS₂ thin films using spectroscopic ellipsometry