▎ 摘　　要

We report on the restoration of the electronic characteristics of wafer-scale chemical,vapor deposition (CVD) monolayer graphene field-effect transistors (GFETs) by reducing the impurity concentration. An optimized electropolishing process on copper foils combined with carbon-fluorine encapsulation using a suitable amorphous fluoropolymer enables reducing the surface roughness of graphene and screening out interfacial impurity scattering, which leads to an improvement in all key device metrics. The conductivity at the Dirac point is substantially reduced, resulting in an, increase in the on-off current ratio. In addition, the field-effect mobility increased from 1817 to 3918 cm(2)/V-s, the impurity concentration decreased from 1.1 x 10(12) to 2.1 x 10(11) cm(-2) and the electron and hole transport became more symmetric. Significantly, favorable shifts toward zero Voltage were observed in the Dirac point. We postulate that the smoother surface due to electropolishing and a pool of strong dipole-dipole moments in the flouropolymer coating provide a charge buffer that relaxes the fluctuation in the electron-hole puddles. We also investigate the long-term stability in GFETs encapsulated with fluoropolymer, which exhibit a high hydrophobicity that suppresses the chemical interaction with water molecules.