Toward selecting optimal support layer for CVD-grown graphene transfer onto arbitrary substrate by surface energy engineering

Transfer methods that exploit the surface tension of the substrate and liquid medium have been developed to obtain high-quality graphene films for various applications. However, when transferring graphene to a substrate, the interaction between the two crucially depends on their respective surface energies; however, the surface energy of support-coated graphene has not been considered in previous studies. In this study, we investigated the characteristics of graphene films transferred onto arbitrary substrates using supporting layers with different surface energies including polymethyl methacrylate, cellulose acetate, and paraffin. Step-by-step monitoring of graphene during the transfer process using Raman spectroscopy revealed that the strain of the graphene film was mainly determined when support-coated graphene was attached to the substrate, and the graphene was highly p-doped by the hydrophilic substrates and support layers. Interestingly, the 2D Raman peaks were narrower when the substrates and support layers with opposite surface polarities were used together compared to those with similar surface polarities because of the weaker adhesion between the two surfaces with opposite surface polarities, demonstrated by density functional theory calculations. These results suggest a way of selecting the optimal support layer by considering the surface energy for graphene transfer to any substrate, determined by the application.