From positive to negative magnetoresistance in graphene with increasing disorder

Artificial disorder was introduced gradually into monolayer graphene by controlling Ga+ ion irradiation and the corresponding electronic transport properties regulated by gate voltage, source-drain voltage, temperature, and magnetic field were studied experimentally. An unsaturated positive magnetoresistance (MR) up to 100% at ∼5 T was observed in as-fabricated graphene, while there is significant negative MR in disordered graphene. This phenomenon was attributed to the monocrystalline breaking and crystallite-boundary scattering in disordered graphene.