Localization of charge carriers in monolayer graphene gradually disordered by ion irradiation

TL;DR

This study investigates how charge carriers in monolayer graphene become localized as disorder increases due to ion irradiation, revealing a transition from weak localization to strong localization and variable-range-hopping conduction.

Contribution

It provides experimental evidence and theoretical analysis of the gradual transition from weak to strong localization in graphene caused by ion-induced disorder.

Findings

Transition from weak localization to strong localization with increased disorder

Observation of crossover from Mott to Efros-Shklovskii VRH regimes

Good agreement between theoretical models and experimental data

Abstract

Gradual localization of charge carriers was studied in a series of micro-size 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 magnetoresistance in fields up to 4 T showed 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 showed a remarkably good agreement with experimental data.