Thermal annealing of graphene to remove polymer residues

The process of graphene transfer generally involves a polymer support. Thermal annealing of graphene monolayers transferred from Cu to SiO2/Si substrate has been investigated to remove polymethyl methacrylate (PMMA) residue. The results show that a clean graphene surface without any deterioration is difficult to obtain by conventional thermal annealing method owing to the reaction between the graphene and the carbon by-products from the residual polymers. Although a higher annealing temperature facilitates removal of the polymer residue on graphene surface, it may also increase the amount of amorphous carbon. In this work, we examine various annealing conditions to remove the polymer residue. Annealing under H2 ambience is effective in removing pendant functional groups in the polymer, yet increases the amorphous carbon also. In case of Ar ambience with high temperature, the polymer residue is efficiently removed without amorphous carbon.