Abstract
The temperature dependence of electric transport properties of single-layer and few-layer graphene at large charge doping is of great interest both for the study of the scattering processes dominating the conductivity at different temperatures and in view of the theoretically predicted possibility to reach the superconducting state in such extreme conditions. Here we present the results obtained in 3-, 4- and 5-layer graphene devices down to 3.5 K, where a large surface charge density up to about 6.8·1014 cm−2 has been reached by employing a novel polymer electrolyte solution for the electrochemical gating. In contrast with recent results obtained in single-layer graphene, the temperature dependence of the sheet resistance between 20 K and 280 K shows a low-temperature dominance of a T2 component – that can be associated with electron-electron scattering – and, at about 100 K, a crossover to the classic electron-phonon regime. Unexpectedly, this crossover does not show any dependence on the induced charge density, i.e. on the large tuning of the Fermi energy.
Highlights
The temperature dependence of electric transport properties of single-layer and few-layer graphene at large charge doping is of great interest both for the study of the scattering processes dominating the conductivity at different temperatures and in view of the theoretically predicted possibility to reach the superconducting state in such extreme conditions
We present the results obtained in 3, 4- and 5-layer graphene devices down to 3.5 K, where a large surface charge density up to about 6.8?1014 cm[22] has been reached by employing a novel polymer electrolyte solution for the electrochemical gating
The transport properties of multi-layer graphene have been experimentally studied[5,6], the electric transport of few-layer graphene (FLG, with number of layers N between 2 and 5) has been much less intensively investigated[7]. This is true when one considers the low-temperature behavior of these transport properties. This information can provide important clues on the scattering processes dominating the conductivity of Few layers graphene (FLG) and on the quantum corrections to the Drude conductivity which may occur at low temperature[3,4]
Summary
In contrast with recent results obtained in single-layer graphene, the temperature dependence of the sheet resistance between 20 K and 280 K shows a low-temperature dominance of a T2 component – that can be associated with electron-electron scattering – and, at about 100 K, a crossover to the classic electron-phonon regime This crossover does not show any dependence on the induced charge density, i.e. on the large tuning of the Fermi energy. VHSs in double 3- and 4-layer graphene devices have been exploited to enhance critical temperature and onset density of the electron-hole superfluid transition[20] For this reason, even in absence of precise model predictions for superconductivity in FLG, we thought it was worthwhile to perform electric transport measurements in FLG at low temperature and high doping. No trace of superconducting transition has been found in these experiments, but the sheet resistances in the temperature range 20–280 K reproducibly show a peculiar behavior with a dominant low-temperature T2 component and a crossover to the classic electron-phonon linear regime at about 90–100 K, independently of the strong Fermi energy tuning produced by the electrochemical gating
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