Transfer induced compressive strain in graphene: Evidence from Raman spectroscopic mapping

• We investigate the Raman spectrum of CVD graphene before and after transfer.
• Comparison of transferred CVD graphene on SiO2 and exfoliated graphene using Raman spectroscopy.
• Strain and doping investigation of CVD graphene and exfoliated graphene.

We have used spatially resolved micro Raman spectroscopy to map the full width at half maximum (FWHM) of the graphene G-band and the 2D and G peak positions, for as-grown graphene on copper catalyst layers, for transferred CVD graphene and for micromechanically exfoliated graphene, in order to characterize the effects of a transfer process on graphene properties. Here we use the FWHM(G) as an indicator of the doping level of graphene, and the ratio of the shifts in the 2D and G bands as an indicator of strain. We find that the transfer process introduces an isotropic, spatially uniform, compressive strain in graphene, and increases the carrier concentration.

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