Resistance switching of graphene by gate-controlled polarization reorientation of polyvinylidene fluoride in a field effect transistor

Abstract

Ferroelectric β-phase crystals of a polyvinylidene fluoride (PVDF) polymer grown or deposited on a graphene channel of a field effect transistor would induce various degrees of electrostatic doping (i.e., various amounts of charge carriers) into graphene and in turn ON/OFF switching of the device, only if the electric field applied at the gate can reorient its polarization (i.e., the well-aligned F-to-H dipole moments perpendicular to the all-trans polymer backbone) around the polymer backbone. To assess the feasibility of achieving a β-PVDF/graphene ferroelectric field effect transistor or memory device, we mimic (1) the electric-field-controlled PVDF polarization reversal (with density functional theory calculations and molecular dynamics simulations) and (2) the conductance switching of β-PVDF/graphene by PVDF reorientations (F-, H- and FH-down) representing a cycle of gate-voltage sweep (with density functional theory combined with non-equilibrium Green's function formalism). The low energy barrier of the collective synchronous PVDF chain rotation around the backbone (0.22 eV per monomer) and the high electric field required to initiate the chain rotation (16 V nm⁻¹) are compatible with the domain nucleation-growth theory and would support the polarization-induced resistance switching mechanism if the PVDF film is ultrathin and partially amorphous.