Temperature-dependent Raman spectroscopy studies of 1–5-layer WSe2

Li, Zhonglin; Wang, Yingying; Jiang, Jie; Liang, Yao; Zhong, Bo; Zhang, Hong; Yu, Kai; Kan, Guangfeng; Zou, Mingqiang

doi:10.1007/s12274-020-2669-0

Cited by 51 publications

(31 citation statements)

References 29 publications

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“…2d. Although the overall T dependence is not linear 55 , in the 78–295 K range we get: where k is the slope. This corresponds to a shift of ~0.2 meV in the 78–295 K range.…”

Section: Methodsmentioning

confidence: 87%

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Efficient phonon cascades in WSe2 monolayers

et al. 2021

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Energy relaxation of photo-excited charge carriers is of significant fundamental interest and crucial for the performance of monolayer transition metal dichalcogenides in optoelectronics. The primary stages of carrier relaxation affect a plethora of subsequent physical mechanisms. Here we measure light scattering and emission in tungsten diselenide monolayers close to the laser excitation energy (down to ~0.6 meV). We reveal a series of periodic maxima in the hot photoluminescence intensity, stemming from energy states higher than the A-exciton state. We find a period ~15 meV for 7 peaks below (Stokes) and 5 peaks above (anti-Stokes) the laser excitation energy, with a strong temperature dependence. These are assigned to phonon cascades, whereby carriers undergo phonon-induced transitions between real states above the free-carrier gap with a probability of radiative recombination at each step. We infer that intermediate states in the conduction band at the Λ-valley of the Brillouin zone participate in the cascade process of tungsten diselenide monolayers. This provides a fundamental understanding of the first stages of carrier–phonon interaction, useful for optoelectronic applications of layered semiconductors.

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“…2d. Although the overall T dependence is not linear 55 , in the 78–295 K range we get: where k is the slope. This corresponds to a shift of ~0.2 meV in the 78–295 K range.…”

Section: Methodsmentioning

confidence: 87%

“…3c . Thermal effects are expected to modify the phonon energies 55 . However, in the 78–298 K range we do not observe any measurable shifts in the position of the hot PL peaks, because the shifts induced by acoustic phonons are smaller compared to our experimental error, as discussed in Methods.…”

Section: Resultsmentioning

confidence: 99%

Efficient phonon cascades in WSe2 monolayers

et al. 2021

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“…Figure S3, Supporting Information, shows the temperature dependence of A 1 mode full width at half-maximum (FWHM), in which the line width increased with the temperature because of the transformation of the zone center from optical phonon to acoustic phonon. [44][45][46][47] What's more, we observed the PL intensity of SiP decreased with the increase of temperature (Figure 2c), which is attributed to the shortened non-radiative lifetime by the thermal activation. [48] According to the fitting equation as shown in the inset of Figure 2d, the activation energy (Ea) was calculated to be 29.2 meV, which indicated that the SiP mostly generated the free carries than excitons under optical excitation.…”

Section: High Quality Layered 2d Sipmentioning

confidence: 93%

Low‐Symmetry and Nontoxic 2D SiP with Strong Polarization‐Sensitivity and Fast Photodetection

Zhao

Luo

Yang

et al. 2021

Advanced Optical Materials

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The in‐plane anisotropic feature of 2D layered materials has captured enormous research interest due to their application in polarization‐sensitive photodetection. Here, silicon phosphide (SiP), as a novel member of group IV–V 2D materials, is first introduced to the anisotropic 2D materials family with a high in‐plane anisotropy. The low‐symmetry structure, optical and optoelectronic properties are investigated systematically. Impressively, the photodetectors based on 2D SiP demonstrate high performance with low dark current, a fast response speed of 30 µs, and a strong anisotropic photoresponse with an anisotropic factor of 2.9. Furthermore, a strong polarization‐sensitive photodetector with a dichroic ratio up to 2.3 is realized based on the intrinsic linear dichroism of 2D SiP. This work not only provides an insight into the in‐plane anisotropic properties of 2D SiP, but also sheds light on its great potentials in anisotropic optoelectronic applications.

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“…Raman spectroscopy provides a powerful and non‐destructive technique to probe the phonon and thermal properties. In the past, it has been successfully utilized to investigate the phonon anharmonicity of various crystals such as monocrystalline anatase, [ 15 ] PdO, [ 16 ] PdS, [ 17 ] WS 2, [ 18 ] MoSe 2, [ 19 ] MoS 2 , [ 20 ] and WSe 2 [ 21 ] . By monitoring the wavenumber shift or variation of linewidth of specific Raman modes as a function of temperature, one can evaluate the lattice anharmonic effect.…”

Section: Introductionmentioning

confidence: 99%

Phonon anharmonicity of thermoelectric material HfTe₅ studied by Raman spectroscopy

Xie

et al. 2021

J Raman Spectroscopy

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The understanding of phonon–phonon anharmonic effect in HfTe5 is essential not only for fundamental scientific interest but also for its potential thermoelectric applications. Here, rectangular ribbon‐shaped HfTe5 single crystals have been grown. Raman spectroscopy is further utilized to investigate the phonon anharmonicity of HfTe5 by quantifying the temperature dependence of the phonon mode softening and broadening. We focus on the temperature range from 80 up to 400 K since obvious surface oxidation occurs at higher temperatures. It is found that four phonon anharmonic effects are non‐negligible. The phonon lifetime is greatly reduced by the enhancement of phonon scattering, resulting in the low thermal conductivity in HfTe5 single crystals.

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Temperature-dependent Raman spectroscopy studies of 1–5-layer WSe2

Cited by 51 publications

References 29 publications

Efficient phonon cascades in WSe2 monolayers

Efficient phonon cascades in WSe2 monolayers

Low‐Symmetry and Nontoxic 2D SiP with Strong Polarization‐Sensitivity and Fast Photodetection

Phonon anharmonicity of thermoelectric material HfTe₅ studied by Raman spectroscopy

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Temperature-dependent Raman spectroscopy studies of 1–5-layer WSe2

Cited by 51 publications

References 29 publications

Efficient phonon cascades in WSe2 monolayers

Efficient phonon cascades in WSe2 monolayers

Low‐Symmetry and Nontoxic 2D SiP with Strong Polarization‐Sensitivity and Fast Photodetection

Phonon anharmonicity of thermoelectric material HfTe5 studied by Raman spectroscopy

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Phonon anharmonicity of thermoelectric material HfTe₅ studied by Raman spectroscopy