Raman spectroscopy of graphene at high pressure: Effects of the substrate and the pressure transmitting media

Abstract

The pressure evolution of the Raman spectrum of graphene grown by chemical vapor deposition on polycrystalline copper is investigated with the use of polar and nonpolar pressure transmitting media (PTM). The $G$ and 2$D$ Raman bands exhibit similar pressure slopes for both PTM irrespective of any unintentional initial doping and/or strain of the samples. Our analysis suggests that any pressure-induced charge transfer effects are too small to influence the pressure response of graphene; rather, it is determined by the compressibility of the substrate and the graphene interaction with the substrate and the PTM. For the nonpolar PTM, a peculiar pressure behavior of graphene is observed in the PTM solidification regime, which resembles that of freestanding graphene.