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 E-2g(2), E-2g(1), 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 E-2g(1) mode is insensitive to the anharmonic effect, whereas the E-2g(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.