  Electron beam exposure is a commonly used tool for fabricating and imaging
graphene-based devices. Here we present a study of the effects of electron-beam
irradiation on the electronic transport properties of graphene and the
operation of graphene field-effect transistors (GFET). Exposure to a 30 keV
electron-beam caused negative shifts in the charge-neutral point (CNP) of the
GFET, interpreted as due to n-doping in the graphene from the interaction of
the energetic electron beam with the substrate. The shift of the CNP is
substantially reduced for suspended graphene devices. The electron beam is seen
to also decrease the carrier mobilities and minimum conductivity, indicating
defects created in the graphene. The findings are valuable for understanding
the effects of radiation damage on graphene and for the development of
radiation-hard graphene-based electronics.
