Theoretical study of Raman scattering in MoS2xSe2(1 − x) layered alloys

Two-dimensional layered crystals have attracted great attention due to their unique properties and practical interests for the application in nano-optoelectronics. This work theoretically studies the effect of intralayer interaction on the Raman scattering in MoS2xSe2(1 - x) layered alloy, in particular, the change of intensity and position of the in-plane and out-of-plane mode bands as a function of the concentration of S or Se atoms. The theory of Raman scattering in the layered alloys is developed, where the Green's function method is used to obtain the Raman scattering intensity. The Raman intensity is a function of the concentration of S or Se atoms in the layers and also a function of the parameters of intralayer and interlayer interactions. The modeling and numerical calculations show that the Raman spectrum mostly depends on the parameter describing the intralayer interaction between the unit cells containing S or Se atoms in the layer. The spectrum exhibits the two-mode character when the intralayer interaction is weak while conserves the one-mode character when the intralayer interaction increases to be comparable with the wavenumber position of the bands. The developed microscopic theoretical approach is versatile and can also be applied to interpret Raman spectra and explain some of their features in bulk and two-dimensional layered alloys.