Theoretical and experimental Raman study of molybdenum disulfide

Abstract High pressure Raman spectra were measured for 2H–MoS2 at small pressure intervals, including Stokes Raman spectra from 0 to 40 GPa and anti-Stokes Raman spectra from 0 to 31.4 GPa. Analysis of the pressure-dependent frequencies and full width at half maximums for the A1g and E 2 g 1 modes showed that the A1g mode was more sensitive to pressure. The peaks of the E 2 g 1 mode split from 20.0 GPa, thereby indicating the beginning of a phase transition from 2Hc to 2Ha, and the transition was complete near 40.7 GPa. In the same pressure range, density functional theory calculations confirmed the phase transition and the pressure-dependent frequencies were in good agreement with the experimental results. Simulations predicted that the linear growth in the frequency of A1g-2Hc with the pressure was inhibited at 35 GPa by repulsive interlayer interactions, thereby causing frequency splitting from the A1g-2Ha mode. In addition, the in-plane E 2 g 1 mode of the 2Hc phase was annihilated when the pressure reached 40.7 GPa. Based on our results and previous research, we propose that the 2Hc-2Ha phase transition of MoS2 is complete at around 40.7 GPa and this explains the absence of the Raman peak split for the out-of-plane A1g mode.