Phonon polarization deformation in graphene induced by substrate coupling strengths

Displacement in the Raman shift of conventional Raman spectroscopy usually includes an increase in the number of material layers or a strain variation. To distinguish them, polarization-resolved Raman spectroscopy provides an additional degree of freedom to resolve it. In this work, strained graphene induced by different substrates on G band and 2D band phonon modes is studied by polarization-resolved Raman spectroscopy and verified by numerical analysis using Raman tensors and optical Jones calculus. For the strained graphene case, polarization properties of scattered light are obviously different from that in the case of unstrained graphene. Deformation of phonon polarization is seen to originate from different strengths of substrate coupling. This research provides an efficient quantitative method to explore any distortion of strain anisotropy in two-dimensional materials, which is important for the development of straintronics in the future.