Doping Graphene with Ferroelectric beta-PVDF Polymer Film: Density Functional Theory Calculation and Molecular Dynamics Simulation
N Lee and J Lee and T Ryu and Y Kim and Y Lansac and YH Jang, SCIENCE OF ADVANCED MATERIALS, 6, 2422-2427 (2014).
Graphene is a promising channel material for field-effect transistors and non-volatile memories owing to its high carrier mobility, but its zero band gap hampers the realization of such carbon-based devices. Doping graphene with a thin-film deposition of ferroelectric polymer such as polyvinylidene fluoride (PVDF) has been suggested as a solution to increase their ON/OFF ratio, but the origin of the amplified resistance switching in this PVDF/graphene-based device is still unclear. As a step to better understanding the mechanism at the molecular level, we herein carry out density functional theory calculations on the doping characteristics of a PVDF thin film on a single-layer graphene as a function of the polarization direction of PVDF and relate it to the carrier concentration and the resistance states of the graphene channel. From this, we propose a new architecture for the PVDF/graphene-based field-effect transistors and non-volatile memories. Since the beta-phase is the only PVDF phase whose permanent polarization can make it useful for ferroelectric applications, we carry out molecular dynamics (MD) simulations to confirm the formation of beta-like phases from amorphous PVDF under a shear stress often applied during device fabrication.
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