Remote doping of graphene on SiO2 with 5 keV x-rays in air

The transport properties of graphene change strongly in the presence of electric fields due to graphene's band structure. This makes graphene sensitive to charges in an insulator substrate. Graphene on SiO2/Si is studied under x-ray irradiation in ambient conditions. Using the metal oxide semiconductor structure of their samples, the authors observe remote doping due to the creation of positive charges in the oxide by the irradiation and relate them to resistance and Hall effect measurements performed on the graphene gate. The observed changes in conductivity, Hall charge carrier density, and the corresponding charge carrier mobility are consistent with expectations as well as recent experiments using graphene field effect transistors under ultrahigh vacuum conditions [P. Prochazka et al. Sci. Rep. 7, 563 (2017)]. Furthermore, the stability of the effect under ambient conditions and its recovery using thermal annealing is demonstrated.