Solvent-free transfer of monolayer graphene with recrystallized cyclododecane

Graphene produced by chemical vapor deposition finds applications in a wide range of technologies. However, the transfer of monolayer graphene from the native substrate (commonly Cu foils) to a desired substrate remains challenging. In this study, we report a solvent-free transfer technique for monolayer graphene using a sublimable supporting coating, cyclododecane (CDD). After spin-coating CDD on graphene grown on Cu foil, we rapidly heat the stack at 80 °C to melt and recrystallize the CDD coating. The recrystallized coating top surface becomes composed of larger and interconnected CDD crystals, which form a mechanically strong coating that takes almost 2 h to sublimate completely. Having a bottom surface that closely conforms to graphene's topography, the CDD coating can effectively support graphene during the whole transfer process without compromising its structural integrity, maintaining its superior electrical and optical properties. In this way, CDD becomes capable of transferring monolayer graphene over square centimeter areas. Unlike traditional polymer-based techniques, after transfer, the CDD coating sublimates completely, without the need of any post-transfer cleaning treatment. Our work shows that the CDD coating can be an alternative transfer medium for the efficient and clean transfer of monolayer graphene. This technique paves the way for the widespread adoption of graphene in various applications, including those not compatible with solvents.