Abstract
The temperature effect on the Raman scattering efficiency is investigated in varepsilon-GaSe and gamma-InSe crystals. We found that varying the temperature over a broad range from 5 to 350 K permits to achieve both the resonant conditions and the antiresonance behaviour in Raman scattering of the studied materials. The resonant conditions of Raman scattering are observed at about 270 K under the 1.96 eV excitation for GaSe due to the energy proximity of the optical band gap. In the case of InSe, the resonant Raman spectra are apparent at about 50 and 270 K under correspondingly the 2.41 eV and 2.54 eV excitations as a result of the energy proximity of the so-called B transition. Interestingly, the observed resonances for both materials are followed by an antiresonance behaviour noticeable at higher temperatures than the detected resonances. The significant variations of phonon-modes intensities can be explained in terms of electron-phonon coupling and quantum interference of contributions from different points of the Brillouin zone.
Highlights
The temperature effect on the Raman scattering efficiency is investigated in ε-GaSe and γ-InSe crystals
A significant antiresonance behaviour accompanies the resonances at higher temperatures, which leads to the vanishing of the modes intensities
The observed effects are discussed in terms of electron-phonon coupling and quantum interference of contributions from different points of the Brillouin zone (BZ)
Summary
The temperature effect on the Raman scattering efficiency is investigated in ε-GaSe and γ-InSe crystals. The resonant conditions of Raman scattering are observed at about 270 K under the 1.96 eV excitation for GaSe due to the energy proximity of the optical band gap. The main focus of researchers has been on semiconducting transition metal dichalcogenides (S-TMDs), e.g. MoS2 , WSe2 , and MoTe23,4 Another much larger group of layered materials, i.e. semiconducting post-transition metal chalcogenides (S-PTMCs), e.g. SnS, GaS, InSe, and GaTe, has drawn the attention of the 2D community. The resonant excitation may lead to a significant enhancement of the RS intensity in S-TMD as well as the activation of otherwise inactive modes This offers supplementary information on the coupling of particular phonons to electronic transitions of a specific s ymmetry[19,20,21]. The observed effects are discussed in terms of electron-phonon coupling and quantum interference of contributions from different points of the Brillouin zone (BZ)
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