Temperature dependent photoluminescence from WS2 nanostructures

Sharma, Satinder K.; Bhagat, Shubham; Singh, Jasvir; Ahmad, Manzoor; Sharma, Sandeep

doi:10.1007/s10854-018-0137-3

Cited by 19 publications

(12 citation statements)

References 32 publications

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“…[41,42] As the temperature decreases to liquid nitrogen temperature (77 K), both the X 0 and T emissions become more intense, which is ascribed to the reduced phonon scattering at low temperature. [43] Also, clear blue-shifts of the peak positions indicated by the black arrows are found for both X 0 and T emissions. Figure 3b shows the peak emission energy of X 0 and T extracted by the dual-Gaussian fitting.…”

Section: Wwwadvopticalmatdementioning

confidence: 83%

Impurity‐Induced Robust Trionic Effect in Layered Violet Phosphorus

Cai

Lai

et al. 2021

Advanced Optical Materials

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such as the strong room-temperature PL and abundant valley-selective excitation of excitonic states in transition metal dichalcogenides (TMDs). [2,[4][5][6][7] Besides, a neutral exciton can capture an additional electron (e) or hole (h) to form a correlated threeparticle state (e-e-h or h-e-h), known as a trion (T), in the presence of excess carriers. [8] It has been demonstrated that trionic effect can strongly affect the PL properties of 2D materials through controlling the excess carriers' population. [9][10][11] However, the small trion binding energy in various TMDs (< 50 meV) greatly hinders the investigation of T emission in 2D systems. Taking the thermal fluctuation and dimensional confinement into account, it is arduous for people to observe T emission in non-monolayer TMDs at room temperature. [12] Recently, the radiative recombination of X 0 and T in black phosphorus (BP) has been studied yet. [13] Robust T emission in monolayer BP was observed at ≈1.63 eV at room temperature with the trion binding energy of ≈100 meV. [14] Although the trion binding energy of BP is considerable, the weak ambient stability, especially for monolayer or bilayer BP, limits its application in future trionic devices. More importantly, subject to the narrow bandgap, the PL emission of BP mainly lies in near-IR range.Violet phosphorus (VP), another allotrope of the elemental phosphorus, was first identified by W. Hittorf in 1865. [15] The subtle van der Waals (vdW) layered phosphorus bi-tubular structure leads to abundant exciton-related phenomena, for example, strong PL emissions in the visible range (from ≈1.67 to ≈2.50 eV) at room temperature. [16][17][18][19][20] Moreover, the thermal stability of VP is higher than that of BP, suggesting that VP and its low-dimensional counterparts are more promising candidates for the research of excitonic physics and optoelectronic applications. [17,21,22] Nevertheless, to the best of our knowledge, the trionic effect in VP have yet to be explored.In this work, we synthesized layered VP crystals by the chemical vapor transport (CVT) method and subsequently studied the trionic effect of the mechanically exfoliated VP flakes comprehensively. We found that a robust T emission contributes to the PL spectra of the VP crystals with a huge trion binding energy of ≈109 meV. Using a mild Ar + plasma post-treatment method, we observed a conversion from T emission to X 0 emission. Trionic effect is a vital excitonic physical phenomenon, which intensively affects the optical and optoelectronic properties of 2D materials. Violet phosphorus (VP) is another allotrope of elemental phosphorus with robust photoluminescence (PL) emission in the visible range. So far, experimental investigations of the excitonic behavior in VP are quite scarce. Herein, the evolution of the PL mechanism in synthesized VP crystals against the Ar + plasma exposure is investigated with emphasis on a conversion from trion to exciton emission. The estimated trion binding energy of VP is ≈109 meV, relatively larger than common la...

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Section: Wwwadvopticalmatdementioning

confidence: 83%

Impurity‐Induced Robust Trionic Effect in Layered Violet Phosphorus

Cai

Lai

et al. 2021

Advanced Optical Materials

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“…36 In addition, a few minor peaks at 226, 298, 324, and 525 cm −1 were also detected, which are consistent with the previous literature and usually occurred in a monolayer or a few layers of WS 2 nanosheets. 35,37 The origin of these peaks is related to the second-order modes, i.e., phonon overtone and combination of E′ mode. 36 The XRD and Raman results also confirmed the presence of the semiconducting 2H phase of the fewlayered WS 2 nanosheets.…”

Section: ■ Experimental Detailsmentioning

confidence: 99%

“…Liang et al have also reported that the frequency difference of 60.31 and 62.18 cm −1 between the A 1g and E 1 2g peaks suggest the formation of single and bilayer WS 2 nanosheets, respectively. 34,35 Berkdemir et al reported the Raman scattering of single and few-layered WS 2 as a function of the number of S−W−S layers, and it was found that the softening of the A 1g mode (419 cm −1 ) also depicts the reduced number of layers which arises from weaker interlayer contributions to the phonon restoring forces. 32 In the present case the difference of the peak positions (E 1 2g and A 1 g ) was about 68 cm −1 , indicating that the sample is made up of few-layered WS 2 nanosheets.…”

Section: ■ Experimental Detailsmentioning

confidence: 99%

Extremely Reduced Dielectric Constant and Band Gap Enhancement in Few-Layered Tungsten Disulfide Nanosheets

Kashyap

Sharma

Pappu

et al. 2022

J. Phys. Chem. Lett.

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Highly crystalline few-layered tungsten disulfide (WS 2 ) nanosheets were synthesized via a cost-effective, low-temperature hydrothermal route. X-ray diffraction and HR-TEM analysis confirmed the formation of hexagonal nanosheets with thickness of ∼6−8 nm. Raman analysis and AFM results confirmed the fewlayered 2H phase of WS 2 nanosheets. The UV−vis study shows absorption peaks at 219 and 271 nm with large band gap value of ∼3.12 eV for WS 2 nanosheets. Surprisingly, WS 2 nanosheets show a dielectric constant of approximately ε′ ≈ 5245, whereas bulk WS 2 material exhibits a dielectric constant of 7482373. An almost 1426fold decrease in the value of dielectric constant for the WS 2 nanosheet is observed. Such an extreme reduction in dielectric constant and observance of large band gap in WS 2 nanosheet were observed for the first time. The present study reveals the excellent and unusual optical and dielectric properties for their potential application in optoelectronic, dielectric, solar, phosphor, and various nanoelectronic devices.

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“…Generally, the PL intensity of an excitonic band in semiconductors is dramatically quenched with an increase in temperature due to thermally activated non-radiative recombination channels because of the increase in electron-phonon interactions. 43,44 The thermal motion and population of the phonons increase with an increase in temperature, resulting in more scattering of photo-generated carriers via the non-radiative recombination process and reduction in the probability of radiative transition, which gives rise to quenching in intensity with an increase in temperature. For instance, quenching in the exciton intensity occurs due to the decaying of excitons into electrons and holes, which also recombine with phonons via a non-radiative recombination process.…”

Section: Resultsmentioning

confidence: 99%

Coupled excitonic quasiparticle-electron–phonon and interlayer coupling in vertically and horizontally aligned MoS₂

Kumar

et al. 2022

J. Mater. Chem. C

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Temperature dependent photoluminescence from WS2 nanostructures

Cited by 19 publications

References 32 publications

Impurity‐Induced Robust Trionic Effect in Layered Violet Phosphorus

Impurity‐Induced Robust Trionic Effect in Layered Violet Phosphorus

Extremely Reduced Dielectric Constant and Band Gap Enhancement in Few-Layered Tungsten Disulfide Nanosheets

Coupled excitonic quasiparticle-electron–phonon and interlayer coupling in vertically and horizontally aligned MoS₂

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Temperature dependent photoluminescence from WS2 nanostructures

Cited by 19 publications

References 32 publications

Impurity‐Induced Robust Trionic Effect in Layered Violet Phosphorus

Impurity‐Induced Robust Trionic Effect in Layered Violet Phosphorus

Extremely Reduced Dielectric Constant and Band Gap Enhancement in Few-Layered Tungsten Disulfide Nanosheets

Coupled excitonic quasiparticle-electron–phonon and interlayer coupling in vertically and horizontally aligned MoS2

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Coupled excitonic quasiparticle-electron–phonon and interlayer coupling in vertically and horizontally aligned MoS₂