Irradiation damage in graphene on SiO2 probed by local mobility measurements

Using a method based on scanning capacitance spectroscopy, local measurements of the electron mean free path (l) and mobility (mu) have been carried out on single layers of graphene (SLG) mechanically exfoliated from highly oriented pyrolytic graphite and deposited on SiO2/Si. Lateral inhomogeneity of l and mu was found both on pristine and ion irradiated SLG with different C ion fluences (from 10(13) to 10(14) cm(-2)), with an increasing spread in the distribution of l and mu for larger fluences. Before irradiation, the spread was explained by the inhomogeneous distribution of charged impurities on SLG surface and/or at the interface with SiO2. After irradiation, lattice vacancies cause a local reduction of mu in the damaged regions.