Temperature dependence of optical properties of monolayer WS2 by spectroscopic ellipsometry

Nguyễn, Hoàng Tùng; Kim, Tae Jung; Park, Han Gyeol; Le, Van Long; Nguyen, Xuan Au; Koo, Dohyoung; Lee, Chul‐Ho; Cuong, Do Duc; Hong, Soon Cheol; Kim, Young Dong

doi:10.1016/j.apsusc.2020.145503

Cited by 24 publications

(22 citation statements)

References 57 publications

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“…In this case, the semiclassical oscillator strength of the bright A-exciton for TMDC monolayers is proportional to the exciton density N / V , exciton resonance energy E 0 , and transition dipole moment μ, i.e., f ∝ NE 0 μ/ V , which jointly determine the exciton oscillator strength . Actually, it has been demonstrated that the oscillator strength of the excitons in the WS 2 monolayer, which is reflected in the absorption of the WS 2 monolayer, can be modified by temperature and substrate through the change in exciton density. , …”

Section: Resultsmentioning

confidence: 98%

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS₂/Au Nanocavity

et al. 2022

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Strong plasmon–exciton coupling, which has potential applications in nanophotonics, plasmonics, and quantum electrodynamics, has been successfully demonstrated by using metallic nanocavities and two-dimensional materials. Dynamical control of plasmon–exciton coupling strength, especially by using optical methods, remains a big challenge although it is highly desirable. Here, we report the optical introduction and manipulation of plasmon–exciton–trion coupling realized in a dielectric–metal hybrid nanocavity, which is composed of a silicon (Si) nanoparticle and a thin gold (Au) film, with an embedded tungsten disulfide (WS2) monolayer. We employ scattering and photoluminescence spectra to characterize the coupling strength between plasmons and excitons in Si/WS2/Au nanocavities constructed by using Si nanoparticles with different diameters. We enhance the plasmon–exciton and plasmon–trion coupling strength by injecting excitons and trions into the WS2 monolayer with a 488 nm laser beam. It is revealed that the emission intensities of excitons and trions with respect to the reference WS2 monolayer can be modified through the change in the coupling strength induced by the laser light. Interestingly, the coupling strength between the plasmons and the excitons/trions can be manipulated from weak to strong coupling regime by simply increasing the laser power, which is clearly resolved in the scattering spectra of Si/WS2/Au nanocavities. More importantly, the plasmon–exciton–trion coupling induced by the laser light is confirmed by the energy exchange between excitons and trions. Our findings indicate the possibility for optically manipulating plasmon–exciton interaction and suggest the practical applications of dielectric–metal hybrid nanocavities in nanoscale plasmonic devices.

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Section: Resultsmentioning

confidence: 98%

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS₂/Au Nanocavity

et al. 2022

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“…The observed behavior was explained based on the partial charge density calculations . In the case of the optical transition energetically above A and B excitons, the transitions at high-symmetry points of the Brillouin zone (BZ) and band nesting were studied only for binary TMD compounds. − Those studies were performed for bulk and atomically thin crystals, primarily using optical modulation spectroscopy and spectroscopic ellipsometry.…”

Section: Introductionmentioning

confidence: 99%

“…The modulation techniques, due to their derivative-like character, allow studying, with great precision, optical transitions that correspond to specific k -points of the BZ. , Such experimental methods, when combined with theoretical calculations of the electronic band structure, mainly based on density functional theory (DFT), are the perfect approach for unambiguous assignment of the optical transition to a given k -point of the BZ of novel semiconductor materials. This approach was applied for group IV, , III–V, , and II–VI , semiconductor alloys and, at present, for, i.e., binary TMD compounds ,, as well as alloys. ,, It was shown that, beyond A and B excitons at the K point of the BZ, studied mainly by photoluminescence (PL), other spectral features are visible . These features, i.e., optical transitions, measured also by modulation techniques such as photoreflectance (PR) or piezoreflectance (PzR), were assigned to the band nesting region and higher energetically lying bands at high-symmetry points of the BZ. , …”

Section: Introductionmentioning

confidence: 99%

“…24 Such experimental methods, when combined with theoretical calculations of the electronic band structure, mainly based on density functional theory (DFT), are the perfect approach for unambiguous assignment of the optical transition to a given kpoint of the BZ of novel semiconductor materials. This approach was applied for group IV, 31,32 III−V, 14,33 and II− VI 34,35 semiconductor alloys and, at present, for, i.e., binary TMD compounds 26,27,29 as well as alloys. 36,17,37 It was shown that, beyond A and B excitons at the K point of the BZ, studied mainly by photoluminescence (PL), other spectral features are visible.…”

Section: ■ Introductionmentioning

confidence: 99%

“…36,17,37 It was shown that, beyond A and B excitons at the K point of the BZ, studied mainly by photoluminescence (PL), other spectral features are visible. 29 These features, i.e., optical transitions, measured also by modulation techniques such as photoreflectance (PR) or piezoreflectance (PzR), were assigned to the band nesting region and higher energetically lying bands at high-symmetry points of the BZ. 24,38 Here, we report on experimental and theoretical studies of the electronic band structure of ∼100 μm-thick and atomically thin Mo 1−x W x Se 2 alloys.…”

Section: ■ Introductionmentioning

confidence: 99%

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Experimental and Theoretical Studies of the Electronic Band Structure of Bulk and Atomically Thin Mo_1–xW_xSe₂ Alloys

Kopaczek

Woźniak

Tamulewicz-Szwajkowska

et al. 2021

ACS Omega

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We present studies focused on the evolution of the electronic band structure of the Mo 1−x W x Se 2 alloy with the tungsten content, which was conducted by combining experimental and theoretical methods. Employed spectroscopic techniques, namely, photoreflectance, photoacoustic spectroscopy, and photoluminescence, allowed observing indirect and direct transitions at high and beyond high-symmetry points of the Brillouin zone (BZ). Two excitons (A and B) associated with the K point of the BZ were observed together with other optical transitions (C and D) related to band nesting. Moreover, we have also identified the indirect transition for the studied crystals. Obtained energies for all transitions were tracked with a tungsten content and compared with results of calculations performed within density functional theory. Furthermore, based on the mentioned comparison, optical transitions were assigned to specific regions of the BZ. Finally, we have obtained bowing parameters for experimentally observed features, for, i.e., thin-film samples: b(A) = 0.13 ± 0.03 eV, b(B) = 0.14 ± 0.03 eV, b(C) = 0.044 ± 0.008 eV, and b(D) = 0.010 ± 0.003 eV.

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The Role of Additives in Suppressing the Degradation of Liquid‐Exfoliated WS₂ Monolayers

et al. 2021

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Group VI transition metal dichalcogenides (TMDs) are considered to be chemically widely inert, but recent reports point toward an oxidation of monolayered sheets in ambient conditions, due to defects. To date, the degradation of monolayered TMDs is only studied on individual, substrate‐supported nanosheets with varying defect type and concentration, strain, and in an inhomogeneous environment. Here, degradation kinetics of WS2 nanosheet ensembles in the liquid phase are investigated through photoluminescence measurements, which selectively probe the monolayers. Monolayer‐enriched WS2 dispersions are produced with varying lateral sizes in the two common surfactant stabilizers sodium cholate (SC) and sodium dodecyl sulfate (SDS). Well‐defined degradation kinetics are observed, which enable the determination of activation energies of the degradation and decouple photoinduced and thermal degradation. The thermal degradation is slower than the photoinduced degradation and requires higher activation energy. Using SC as surfactant, it is sufficiently suppressed. The photoinduced degradation can be widely prevented through chemical passivation achieved through the addition of cysteine which, on the one hand, coordinates to defects on the nanosheets and, on the other hand, stabilizes oxides on the surface, which shield the nanosheets from further degradation.

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Temperature dependence of optical properties of monolayer WS2 by spectroscopic ellipsometry

Cited by 24 publications

References 57 publications

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS₂/Au Nanocavity

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS₂/Au Nanocavity

Experimental and Theoretical Studies of the Electronic Band Structure of Bulk and Atomically Thin Mo_1–xW_xSe₂ Alloys

The Role of Additives in Suppressing the Degradation of Liquid‐Exfoliated WS₂ Monolayers

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Temperature dependence of optical properties of monolayer WS2 by spectroscopic ellipsometry

Cited by 24 publications

References 57 publications

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS2/Au Nanocavity

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS2/Au Nanocavity

Experimental and Theoretical Studies of the Electronic Band Structure of Bulk and Atomically Thin Mo1–xWxSe2 Alloys

The Role of Additives in Suppressing the Degradation of Liquid‐Exfoliated WS2 Monolayers

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Product

Resources

About

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS₂/Au Nanocavity

Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS₂/Au Nanocavity

Experimental and Theoretical Studies of the Electronic Band Structure of Bulk and Atomically Thin Mo_1–xW_xSe₂ Alloys

The Role of Additives in Suppressing the Degradation of Liquid‐Exfoliated WS₂ Monolayers