Raman Scattering and Infrared Reflectance in 2H-MoSe₂

Abstract

Raman scattering and infrared reflectance have been measured in 2H-MoSe 2 . We observed all Raman-active modes, A 1g , E 1g , E 2g 1 and E 2g 2 , and two infrared-active modes, E 1u 2 and A 2u 2 . Intralayer force constants are estimated from the central force model. The bond between metal (Mo) and chalcogen (Se) predominates over the high-lying phonon frequencies with long wavelength. On the other hand, interlayer shear force constant is estimated from the frequency of E 2g 2 mode, that is a rigid-layer mode, and is much smaller than the intralayer force constants. This fact, which is similar to that in other group VIB transition-metal dichalcogenides, reflects that the interlayer interaction is due to van der Waals force. The second-order Raman spectrum has been also observed and discussed.