▎ 摘　　要

The effects of encapsulating graphene with poly(methyl methacrylate) (PMMA) polymer are determined through in situ electrical transport measurements. After regenerating graphene devices in dry-nitrogen environments, PMMA is applied to their surfaces. Low-temperature annealing decreases the overall doping level, suggesting that residual solvent plays an important role in the doping. For few-layer graphene devices, we even observe stable n-doping through annealing. Application of solvent onto encapsulated devices demonstrates enhanced hysteric switching between p and n-doped states. The stability and ubiquitous use of PMMA in nanolithography make this polymer a potentially useful localized doping agent for graphene and other two-dimensional materials. (C) 2013 AIP Publishing LLC.