Ultraclean Graphene Transfer Using a Sacrificial Fluoropolymer Nanolayer: Implications for Sensor and Electronic Applications

The transfer of chemical vapor deposited (CVD) monolayer graphene by using poly[4,5-difluoro-2,2-bis-(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene] (Teflon AF1600) fluoropolymer (FP) as a sacrificial nanolayer is demonstrated. Owing to the chemical inertness of FPs, the AF1600-assisted transfer produces an ultraclean surface with excellent transfer integrity. Compared with the widely used poly(methyl methacrylate)-assisted transfer, AF1600-assisted transfer produces better overall transfer quality as measured by root-mean-square (RMS) roughness. Adding a noncovalent surface monolayer between the graphene and the FP facilitates the FP removal after graphene transfer, resulting in a surface with RMS roughness of 0.4-0.5 nm due to a better reduction of the surface residue after transfer. The remaining residue is found to be primarily associated with thermal-expansion ripples in the graphene that act as trapping sites for the low-molecular-weight FP particles. This work provides a scalable solution to clean CVD graphene transfer for many applications, particularly in sensors where surface cleanliness is paramount. The use of prefunctionalized graphene via self-assembled monolayers as molecular scale passivation layer could further enhance its utility as an integration scheme for graphene sensors.