Phonon Anharmonicity of Tungsten Disulfide

Abstract

Recent studies demonstrate that 2H-WS2 is an excellent candidate for further applications in the electronics, spintronics, and optoelectronics. The details of phonon scattering processes associated with the thermal properties of a material are crucial for commercial applications. Here, we report an experimental study of the temperature-dependent Raman spectra of 2H-WS2 over a wide range from 3.6 to 850 K. The nonlinear temperature-dependent behavior corresponding to the phonon anharmonicity is estimated from both the frequency and linewidth of E2g 2, E2g 1, and A1g modes. It is found that the three-phonon process is dominant in the phonon softening and linewidth broadening in the whole temperature range. The four-phonon process can be detected and is even stronger than the three-phonon process at high temperatures. The obtained E2g 1 mode is insensitive to the anharmonic effect, whereas the E2g 2 mode is most sensitive. The phonon anharmonicity is suggested to mainly originate from the interaction between acoustic phonon and optical phonon. Understanding the phonon anharmonicity in 2H-WS2 is helpful for further applications of nanodevices.

Phonon anharmonicity of thermoelectric material HfTe5 studied by Raman spectroscopy

“…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.…”

Role of Optical Phonons in Bulk Molybdenum Diselenide Thermal Properties Probed by Advanced Raman Spectroscopy

“…The temperature‐dependent frequency shifts can be interpreted as the contribution of phonon anharmonic effect Δ ω A and thermal expansion of the lattice Δ ω E . Hence, the temperature‐dependent phonon frequency can be expressed as [ 27,37 ] in which Δ ω E ( T ) can be written aswhere T is the Kelvin temperature, ω 0 is the intrinsic frequencies of optical phonons at T = 0 K, γ is the Grüneisen parameter, and α is the thermal expansion coefficient. Ding et al calculated the mode Grüneisen parameters and the thermal expansion coefficient of bulk MoSe 2 using the first‐principles theory.…”

“…The temperature-dependent frequency shifts can be interpreted as the contribution of phonon anharmonic effect Δω A and thermal expansion of the lattice Δω E . Hence, the temperature-dependent phonon frequency can be expressed as [27,37] ωðTÞ ¼ ω 0 þ Δω A ðTÞ þ Δω E ðTÞ (2) in which Δω E (T) can be written as…”

“…Temperature‐dependent Raman spectra are able to extract a phonon anharmonic scattering process from Raman shift and evolution of full‐width at half‐maximum (FWHM), illuminating the thermal transport behaviors in crystals. This method has been widely used to study the anharmonicity of silicon, [ 23 ] graphene, [ 24 ] PdS, [ 25 ] MoS 2 , [ 26 ] WS 2 , [ 27 ] and so on. However, there is a lack of systematic research on the anharmonicity of MoSe 2 over a wide temperature range.…”

Limits of the quasiharmonic approximation in MgO: Volume dependence of optical modes investigated by infrared reflectivity and ab initio calculations

“…However, further refined experiments and advanced calculations are needed to adequately understand multiphonon scattering and its impact on the physical properties of solids [11][12][13][14][15][16].…”