In this thesis, electron beam irradiation effects on the electronic transport properties of graphene have been systematically studied. In situ electron beam irradiation and simultaneous transport measurement techniques were developed and used to characterize the changes of graphene's transport properties at different sample treatment stages. The electron irradiation with precise dosage control under clean vacuum conditions has been shown to induce bond disorder and intervalley scattering in high quality single layer graphene, but not necessarily lattice damage suggested by previous studies. This was evidenced by the changes of temperature-dependent transport properties, quantum Hall effects and large negative magnetoresistance effects observed at cryogenic temperatures. Particul...[ Read more ]

In this thesis, electron beam irradiation effects on the electronic transport properties of graphene have been systematically studied. In situ electron beam irradiation and simultaneous transport measurement techniques were developed and used to characterize the changes of graphene's transport properties at different sample treatment stages. The electron irradiation with precise dosage control under clean vacuum conditions has been shown to induce bond disorder and intervalley scattering in high quality single layer graphene, but not necessarily lattice damage suggested by previous studies. This was evidenced by the changes of temperature-dependent transport properties, quantum Hall effects and large negative magnetoresistance effects observed at cryogenic temperatures. Particularly, a plateau-like feature of the Hall conductivity σ_xy at ν = 0 together with a nonzero longitudinal resistivity ρ_xx were observed in the quantum Hall effect after electron irradiation with mild dosage, which suggested the existence of bond disorder. The bond disorder significantly modified the Raman scattering and the electronic transport properties of graphene, which was consistent with that observed in hydrogenated graphene. The in situ transport measurements at different sample treatment stages also revealed an interesting activation process of graphene through electron beam irradiation. The activated graphene samples were highly and only sensitive to oxygen and water vapors. Only with oxygen and water molecules absorbed would the activated graphene devices show a pronounced p-type unipolar field effect, where the electron conduction was suppressed and the hole conduction was almost unchanged. It has also been shown that this electron irradiation induced activation process of graphene required clean vacuum conditions without hydrocarbon contamination.