▎ 摘　　要

Scanning Kelvin probe microscopy (SKPM) is applied to experimentally understand the asymmetric behaviors in hole and electron transportation regions in graphene field-effect transistors (FETs). With gate modulation, the transition from p-p-p to p-n-p (for a Ag or Pd source/drain junction with graphene) or from n-p-n to n-n-n (for an Al source/drain junction with graphene) is verified by SKPM, which is believed to be responsible for the asymmetric transport. The odd resistance (R-odd) is positive for Ag (or Pd)/single-layer-graphene (SLG) FETs with Delta WFintrinsic > 0, while R-odd is negative for Al/SLG devices with Delta WFintrinsic < 0, where Delta WFintrinsic is defined as the work function difference between metal and intrinsic graphene.