Exciton-dominated Dielectric Function of Atomically Thin MoS2 Films

Yu, Yiling; Yu, Yifei; Cai, Yongqing; Li, Wei; Gürarslan, Alper; Peelaers, Hartwin; Aspnes, D. E.; Walle, Chris G. Van de; Nguyen, Nhan V.; Zhang, Yong‐Wei; Cao, Linyou

doi:10.1038/srep16996

Cited by 163 publications

(201 citation statements)

References 32 publications

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“…The absorbance of the free standing material constitutes in the visible range up to 15% and is reduced by about 1/3 for the monolayers on fused silica [46] . The high absorbance values underline the strong light matter interaction of SC-TMDs even in the monolayer limit with a thickness of less than 1 nm as it has been reported by several theoretical and experimental studies, too [14,22,26,27,[45][46][47][48]122,124,128,130] . The sizeable reduction of the absorbance for monolayers on a substrate points to the fact that the optical response can be significantly altered just by modification of substrate or environment by dielectric engineering and screening effects [38,62,63,65,74,89,127,[131][132][133] .…”

Section: From the Extinction Coefficient In The Visible Range Displaymentioning

confidence: 67%

Light–matter interaction in transition metal dichalcogenides and their heterostructures

Wurstbauer¹,

Miller²,

Parzinger³

et al. 2017

J. Phys. D: Appl. Phys.

102

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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.

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Section: From the Extinction Coefficient In The Visible Range Displaymentioning

confidence: 67%

Light–matter interaction in transition metal dichalcogenides and their heterostructures

Wurstbauer¹,

Miller²,

Parzinger³

et al. 2017

J. Phys. D: Appl. Phys.

102

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“…This large tunability is achieved by leveraging on the strong excitonic effects of the monolayers 16 and the high susceptibility of the excitons to the influence of free charge carriers.…”

mentioning

confidence: 99%

“…The details of the design principle can be found in supplementary information (S2). TMDC materials much 16 unless the changing may induce substantial change in the exciton spectral width or the doping to the materials. 46 More importantly, this result may open up a new age of field-effect photonics whose optical functionality can be electrically controlled in ways similar to that of stateof-art CMOS circuits.…”

mentioning

confidence: 99%

Giant Gating Tunability of Optical Refractive Index in Transition Metal Dichalcogenide Monolayers

Yu¹,

Yu²,

Huang³

et al. 2017

Nano Lett.

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We report that the refractive index of transition metal dichacolgenide (TMDC) monolayers, such as MoS2, WS2, and WSe2, can be substantially tuned by > 60% in the imaginary part and > 20% in the real part around exciton resonances using CMOS-compatible electrical gating. This giant tunablility is rooted in the dominance of excitonic effects in the refractive index of the monolayers and the strong susceptibility of the excitons to the influence of injected charge carriers. The tunability mainly results from the effects of injected charge carriers to broaden the spectral width of excitonic interband transitions and to facilitate the interconversion of neutral and charged excitons. The other effects of the injected charge carriers, such as renormalizing bandgap and changing exciton binding energy, only play negligible roles. We also demonstrate that the atomically thin monolayers, when combined with photonic structures, can enable the efficiencies of optical absorption (reflection) tuned from 40% (60%) to 80% (20%) due to the giant tunability of refractive index. This work may pave the way towards the development of field-effect photonics in which the optical functionality can be controlled with CMOS circuits.

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“…Graphene can be characterized using a surface conductivity material model . Relative dielectric functions of Ag, TiO 2 , and MoS 2 were taken from the experimental reports, respectively.…”

Section: Theoretical Model and Methodsmentioning

confidence: 99%

Plexciton for surface enhanced Raman scattering and emission

Feng

Gao

Wang

et al. 2019

J Raman Spectroscopy

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Plexcitons are polaritonic modes that result from coherently coupled plasmons and excitons. Far‐ and near‐field properties of Ag/semiconductor core–shell nanoparticles on silica‐coated silver substrate were theoretically studied, using finite‐difference time‐domain method. Our calculations suggested that titanium dioxide (TiO2) would be a better coating material, useful for the design of high‐sensitive surface enhanced Raman scattering (SERS) substrate. The calculated Raman enhancement factor could be turned to as high as 4.0 × 1010 under the 633‐nm laser excitation. Surface plasmon‐coupled emission of SERS reveals an optimal collection angle of 5°, which shows a huge back scattering of the studied system. Our theoretical results could be used as a reference for the experimental design of semiconductor‐based SERS substrate with high efficiency.

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Exciton-dominated Dielectric Function of Atomically Thin MoS2 Films

Cited by 163 publications

References 32 publications

Light–matter interaction in transition metal dichalcogenides and their heterostructures

Light–matter interaction in transition metal dichalcogenides and their heterostructures

Giant Gating Tunability of Optical Refractive Index in Transition Metal Dichalcogenide Monolayers

Plexciton for surface enhanced Raman scattering and emission

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