Localization of Charge Carriers in Monolayer Graphene Gradually Disordered by Ion Irradiation

摘要

Gradual localization of charge carriers is studied in a series of microsize samples of monolayer graphene fabricated on the common large scale film and irradiated by different doses of C+ ions with energy 35 keV. Measurements of the temperature dependence of conductivity and magneto-resistance in fields up to 4 T show that at low disorder, the samples are in the regime of weak localization and antilocalization. Further increase of disorder leads to strong localization regime, when conductivity is described by the variable-range-hopping (VRH) mechanism. A crossover from the Mott regime to the Efros-Shklovskii regime of VRH is observed with decreasing temperature. Theoretical analysis of conductivity in both regimes shows a remarkably good agreement with experimental data.