Disorder and de-coherence in graphene probed by low-temperature magneto-transport: weak localization and weak antilocalization

We studied weak localization (WL) and and weak antilocalization (WAL) in a eight-contacts Hall bar made of exfoliated monolayer graphene on Si-SiO2, by means of magneto-transport experiments, at temperatures between 0.3 K and 15 K. At low carrier density (n ≊ 7 × 1011 cm−2) we observed a transition from WL to WAL driven by the increasing of the magnetic field, while at high carrier density (n ≊ 2 × 1012 cm−2) only WL was observable. We analyzed the magnetic field driven WL-WAL transition and we evaluated the temperature dependence of the de-coherence parameters using an alternative method compared to previous studies. The values we obtained were corroborated by a root-mean-square analysis of the amplitude of highly-reproducible universal conductance fluctuations.