Splitting and coupling of lattice modes in the layer compound SnS

Zone-centre optical phonons in the layer crystal SnS have been studied by Raman scattering. The phonons observed for the given polarization configurations are consistent with the predictions of group theory. It is shown that SnS behaves approximately like a two-dimensional crystal. This work suggests that SnS is less anisotropic than GeS and GeSe, which have been studied previously.