▎ 摘　　要

We report a new method of ion implantation for hole doping of graphene in which a layer of polymethyl methacrylate (PMMA) is used as a stopping layer to control the B-ion distribution in the graphene layer. This method is very useful for graphene doping in many aspects because it employs the ion energy comparable to what is commercially used in the semiconductor processes and strongly enhances the doping effect in contrast to the previous studies, resulting from B-ions-induced gating effect. PMMA/graphene/ Cu-foil stacks were implanted with 35 keV B- ions to nominal fluences (phi(B)) of 0.5 -50 x 10(10) cm(-2) at room temperature. The electron/hole mobilities are sharply reduced by doping at phi(B) = 0.5 x 10(10) cm(-2), but above this, they increase with increasing phi(B), as estimated from the Dirac curves. The Raman data and theoretical considerations suggest that the electrical properties of the B-doped graphene are governed by strain effect at low phi(B), but by charge-doping effect at high phi(B). (C) 2017 Elsevier Ltd. All rights reserved.