Optical manipulation of the exciton charge state in single-layer tungsten disulfide

Mitioglu, Anatolie; Plochocka, P.; Jadczak, J.; Escoffier, Walter; Rikken, G. L. J. A.; Kulyuk, L.; Maude, D. K.

doi:10.1103/physrevb.88.245403

Cited by 201 publications

(248 citation statements)

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“…At Raman shifts of 2000-3000 cm −1 (595-633 nm) the PL of WS 2 is clearly discernible in the case of purified WS 2 -Au4.5. Since only ML TMDs show appreciable PL, 45,46 this is consistent with ML enrichment. No changes in the PL peak shape or position are observed from the measurement in liquid dispersion suggesting that the AuNPs have little effect on the optical properties of the TMD in the dispersion.…”

Section: Resultssupporting

confidence: 59%

Production of monolayer-rich gold-decorated 2H–WS2 nanosheets by defect engineering

et al. 2018

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Chemical functionalization of low-dimensional nanostructures has evolved as powerful tool to tailor the materials' properties on demand. For two-dimensional transition metal dichalcogenides, functionalization strategies are mostly limited to the metallic 1T-polytype with only few examples showing a successful derivatization of the semiconducting 2H-polytype. Here, we describe that liquid-exfoliated WS 2 undergoes a spontaneous redox reaction with AuCl 3 . We propose that thiol groups at edges and defects sites reduce the AuCl 3 to Au 0 and are in turn oxidized to disulfides. As a result of the reaction, Au nanoparticles nucleate predominantly at edges with tuneable nanoparticle size and density. The drastic changes in nanosheet mass obtained after high loading with Au nanoparticles can be exploited to enrich the dispersions in laterally large, monolayered nanosheets by simple centrifugation. The optical properties (for example photoluminescence) of the monolayers remain pristine, while the electrocatalytic activity towards the hydrogen evolution reaction is significantly improved.

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Section: Resultssupporting

confidence: 59%

Production of monolayer-rich gold-decorated 2H–WS2 nanosheets by defect engineering

et al. 2018

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“…At low temperature (T = 10 K) PL and RC spectra two distinct transitions, corresponding to the exciton and trion are recorded. Their energy positions are in a good agreement with the previous reports [29][30][31][32]. In PL spectra of MoS 2 an additional line (denoted as L, see also Fig.…”

Section: Resultssupporting

confidence: 80%

“…In contrast, in PL spectra of ternary Mo(S y Se 1−y ) 2 and binary MoS 2 MLs trions dominate in PL spectra at all measured temperatures (T = 7 − 295 K). Confinement to a single layer Coulomb and reduced dielectric screening yields also to strong binding energy of charged excitons in TMDCs [30][31][32][33]. In selenides MoSe 2 and WSe 2 binding energy of an additional electron or hole to a neutral exciton is equal to 30 meV and is comparable with energies of optical phonons [33][34][35][36] which leads to strong coupling of the exciton and trion by exchange of an optical phonon [37].…”

Section: Introductionmentioning

confidence: 78%

“…In monolayers of TMDCs excitons, bound electron-hole pairs (X), exhibit very high binding energies of a few hundreds of meV [22][23][24][25][26][27][28]. In the presence of access carriers charged excitons, trions (T), consisting of two electrons and one hole, or two holes and one electrons are reported [29][30][31][32] in optical spectra of TMDCs MLs. In selenides, MoSe 2 and WSe 2 the photoluminescence intensity of a trion is high at low temperatures but rapidly disappear from the PL spectra with the increase of temperature [32].…”

Section: Introductionmentioning

confidence: 99%

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Photoluminescence Studies of Excitonic Complexes in Atomically Thin Mo(S_ySe_1-y)₂ Alloys

Jadczak

2017

Acta Phys. Pol. A

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Transition metal dichalcogenides show new emergent properties at monolayer thickness, notably strong Coulomb and electron-phonon interactions enable new insight into physics of many body effects. Here, we report photoluminescence and reflectivity contrast measurements of excitons (X) and trions (T) and the Raman spectra of phonons in monolayers of Mo(SySe1−y)2 alloys with sulfur mole content from y = 0 up to y = 1. Binary MoSe2 and ternary Mo(SySe2−y) alloys exhibit contrasting behavior in the temperature evolution of excitons and trions photoluminescence intensity from T = 7 − 295 K. In MoSe2 a trion dominates photoluminescence spectra at low temperatures but exciton dominates photoluminescence at higher temperature. In contrast, in ternary Mo(SySe1−y)2 alloys and MoS2 trions dominate photoluminescence spectra at all measured temperatures, with the trion to exciton photoluminescence intensity ratio increasing with sulfur content. We attribute the strong increase of the trion photoluminescence intensity in Mo(SySe1−y)2 monolayers with increase of sulfur mole content to the significant increase of the two-dimensional electron gas concentration and also to the strong exciton-trion coupling mediated by an optical phonon. We also demonstrate that increasing sulfur content in Mo(SySe1−y)2 alloys stabilizes total photoluminescence intensity at high temperature.

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“…In practice, however, our WS 2 devices do not show such a splitting (see Figure 2d), as it is also the case for many devices reported in the literature. 33,34 Therefore, for this experiment we use a device based on a 3R-stacked MoS 2 bilayer, in which the splitting between excitons and trions could be resolved experimentally (see Figure 4a, black curve). 35 Owing to their stacking, 3R TMD multilayers have broken inversion symmetry regardless of the number of layers 36 and are expected to show a large VHE in all cases.…”

Section: 1113mentioning

confidence: 99%

Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength-Dependent Mapping

Ubrig

Philippi

et al. 2017

Nano Lett.

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The band structure of many semiconducting monolayer transition metal dichalcogenides (TMDs) possesses two degenerate valleys, with equal and opposite Berry curvature. It has been predicted that, when illuminated with circularly polarized light, interband transitions generate an unbalanced non-equilibrium population of electrons and holes in these valleys, resulting in a finite Hall voltage at zero magnetic field when a current flows through the system. This is the so-called valley Hall effect that has recently been observed experimentally. Here, we show that this effect is mediated by photo-generated neutral excitons and charged trions, and not by inter-band transitions generating independent electrons and holes. We further demonstrate an experimental 1 arXiv:1708.06914v2 [cond-mat.mes-hall]

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Optical manipulation of the exciton charge state in single-layer tungsten disulfide

Cited by 201 publications

References 29 publications

Production of monolayer-rich gold-decorated 2H–WS2 nanosheets by defect engineering

Production of monolayer-rich gold-decorated 2H–WS2 nanosheets by defect engineering

Photoluminescence Studies of Excitonic Complexes in Atomically Thin Mo(S_ySe_1-y)₂ Alloys

Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength-Dependent Mapping

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Optical manipulation of the exciton charge state in single-layer tungsten disulfide

Cited by 201 publications

References 29 publications

Production of monolayer-rich gold-decorated 2H–WS2 nanosheets by defect engineering

Production of monolayer-rich gold-decorated 2H–WS2 nanosheets by defect engineering

Photoluminescence Studies of Excitonic Complexes in Atomically Thin Mo(SySe1-y)2 Alloys

Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength-Dependent Mapping

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Photoluminescence Studies of Excitonic Complexes in Atomically Thin Mo(S_ySe_1-y)₂ Alloys