Liquids relax and unify strain in graphene

Solid substrates often induce non-uniform strain and doping in graphene monolayer, altering intrinsic properties and reducing carrier mobilities. Using confocal Raman spectroscopy on CVD-grown graphene free-floating on water and at water/liquid interfaces, the authors show that liquid supports relieve preexisting strain, have negligible doping effect, and restore uniformity across the graphene sheet. The effect arises from liquids’ structural adaptability, reduced contamination, and weaker intermolecular bonding, independent of liquid chemistry. Water also enables distinguishing chemical defects from substrate-induced defects in hydrogenated graphene. Liquid supports are thus advantageous over solid supports for applications requiring accurate monitoring of graphene structure upon chemical modification.