Raman scattering studies of graphene under high pressure
Résumé
The effect of pressure – by definition a 3-dimensional concept – on 2-dimensional systems brings a number of fundamentalquestions, which have been partly answered through newly engineered samples and experimental setups. In this review of thehigh-pressure Raman studies of graphene, we will in particular underline the importance of the presence of a supporting substrateand its role for the production of biaxial strain conditions in high pressure experiments. Raman shifts observed during theseexperiments may be related to the strain induced by the substrate rather than by the applied pressure, graphene stress, andhydrostatic pressure not being straightforwardly equivalent in this case of a composite 2D-on-3D material. We will also considerthe effects of the nature of the substrate surface, the nature of the pressure transmittingmedia, aswell as the effect of the numberof layers on the high-pressure response of the 2D–system, by using the phonon behavior as strain probe as pressure is applied.The effects of adhesion and of strain transfer from the substrate to the 2D–system will be at the heart of our discussion.