We demonstrate homogeneous and air-stable n-type doping of graphene grown by thermal chemical vapor deposition. Laminated Polyethyleneimine (PEI) layers fabricated by a simple polymer solution coating were employed. The doping stability of multiple laminated structures (graphene/PEI, PEI/graphene, and graphene/PEI/graphene) was systematically investigated. The resulting graphene/PEI/graphene laminated structure was highly stable in air. Moreover, the work function and carrier concentration of doped graphene can be tuned by altering the laminated structure.
