Direct observation of PMMA removal from graphene surface

PMMA is often used as a carrier layer for transfer of CVD graphene from copper to other substrates. After transfer, the PMMA is removed by chemical or thermal treatment. However, regardless of the method used, polymer residues are left on the graphene surface, which degrade the performance of graphene-based devices. Here, we present a systematic study of PMMA removal after graphene transfer. Raman and FET measurements were applied to monitor the polymer dissolution in an acetone bath. Isotope labeling and in-situ TOF-SIMS, XPS, Raman and AFM all show chemical changes in surface residues upon vacuum annealing. These data along with strategies to clean the graphene surface will be presented.