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

TL;DR

This study investigates how the Raman spectrum of CVD-grown graphene on copper responds to high pressure using different pressure transmitting media, revealing substrate effects and minimal charge transfer influence.

Contribution

It provides new insights into the pressure-dependent Raman response of graphene, highlighting substrate and PTM interactions and their effects on spectral features.

Findings

G and 2D bands have similar pressure slopes regardless of PTM

Charge transfer effects are negligible under pressure

Graphene exhibits free-standing behavior during PTM solidification

Abstract

The pressure evolution of the Raman spectrum of graphene grown by chemical vapour deposition on polycrystalline copper is investigated with the use of a polar and a non-polar pressure transmitting medium (PTM). The G and 2D Raman bands exhibit similar pressure slopes for both PTM irrespectively of any unintentional initial doping and/or strain of the samples. Our analysis suggests that any pressure-induced charge transfer effects are negligibly small to influence the pressure response of graphene. This is determined by the mechanical stress due to the pressure-induced substrate contraction and the transfer efficiency of the latter to the graphene layer, as well as the PTM-graphene interaction. For the non-polar PTM, a peculiar pressure behavior of graphene is observed in the PTM solidification regime, resembling that of free standing graphene.