Phonon Anharmonicity of Tungsten Disulfide

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 E2g2, E2g1, and A_1g 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 E2g1 mode is insensitive to the anharmonic effect, whereas the E2g2 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.