Contact resistance and channel conductance of graphene field-effect transistors under low-energy electron irradiation

We studied the effects of low-energy electron beam irradiation up to 10 keV on graphene-based field effect transistors. We fabricated metallic bilayer electrodes to contact mono-and bi-layer graphene flakes on SiO2, obtaining specific contact resistivity ρc≈ 19 kΩ µm2 and carrier mobility as high as 4000 cm2·V-1·s-1. By using a highly doped p-Si/SiO2 substrate as the back gate, we analyzed the transport properties of the device and the dependence on the pressure and on the electron bombardment. We demonstrate herein that low energy irradiation is detrimental to the transistor current capability, resulting in an increase in contact resistance and a reduction in carrier mobility, even at electron doses as low as 30 e-/nm2. We also show that irradiated devices recover their pristine state after few repeated electrical measurements.