Nonlinear electrical transport in Fe3O4-decorated graphene nanoplatelets

Abstract

This paper investigates the nonlinear properties of graphene nanoplatelets (GNPs), decorated with Fe3O4 magnetic nanoparticles (MaNPs). Nanocomposite MaNP/GNP samples were prepared by a solvothermal method with three different MaNP loading concentrations of 17 wt%, 28 wt% and 40 wt%, and deposited on a metallic interdigitated electrode (IDE). Three different models are proposed to assess measurements, with the objective to explain the electronic transport in the nanocomposites. At first, a thermionic transport model is proposed to fit the DC nonlinear current–voltage characteristics for the three concentrations. It is observed that the barrier height decreases to 0.312, 0.310 and 0.281 eV, following a decrease in the MaNP loading. A second model, dynamic random resistor network (DRRN) further shows that the impedance of IDE increases following the decreasing MaNP loading rate, 40 wt% > 28 wt% > 17 wt%, and that charge transport takes place through a resistor–capacitor (RC) rectifying percolating network. Finally, impedance spectroscopy performed at different applied DC biases shows that a constant phase element (CPE) is necessary in the equivalent circuit in order to fit the Cole–Cole plot AC response of the IDE, instead of the classical parallel RC circuit. The presence of the CPE confirms the hypothesis of random phenomena occurring in the transport according to the DRRN model. CPE is associated with a spatial distribution of different RC circuits, due to disorderness that arises from inhomogeneities in the Fe3O4–GNP samples.