Giant negative magnetoresistance and a transition from strong to weak localization in hydrogenated graphene

Abstract

A giant negative magnetoresistance of up to 28$%$ at 2.5 T is observed in plasma hydrogenated graphene at the charge neutrality point without any sign of saturation at 2.0 K. A detailed analysis of the gate voltage dependence demonstrates a suppression of the giant negative magnetoresistance, which is accompanied by a crossover from strong localization at low carrier concentrations to weak localization at higher carrier concentrations. Evidence of asymmetry in the electron/hole transport is found in the magnetic field traces at low temperature. The asymmetrical transport is attributed to charge transfer processes at the graphene/metal interface and demonstrates the effect of using invasive contact geometries in hydrogenated graphene devices.