A Physics-Based Model of Two-Dimensional Ferroelectric Tunnel Junction With Monolayer and Multilayer Graphene Electrodes

We present a physics-based model of two-dimensional (2D) ferroelectric tunnel junction (FTJ) using a metal-ferroelectric-graphene (MFGr) heterojunction. The electrostatics are self-consistently solved to account for the interplay between the polarization and the screening charges forming on the metal and graphene electrode. This physical model captures the changes in average barrier height originating from the large Fermi level shift in graphene induced by polarization reversal, and also depicts the effects of graphene layer number on the performance of multilayer graphene electrodes. Owing to the low density of states in graphene near its Dirac point and its small quantum capacitance, this Fermi level shift can approach 0.9 eV in monolayer graphene, leading to a giant tunneling electroresistance (TER) ratio. However, such Fermi level shift decreases with layer number increasing, thereby resulting in a decrease in TER ratio. These results provide theoretical guidance and design solutions for further experimental exploration of novel ferroelectric memory based on the 2D ferroelectric and graphene.