Giant Tunneling Electroresistance with Low Resistance-Area in Bilayer Nb2NF2 Nanosheet Ferroelectric Tunnel Junctions

Abstract

Conventional van der Waals ferroelectric tunnel junctions (FTJs), consisting of a two-dimensional (2D) semiconducting ferroelectric tunneling barrier, have undergone extensive experimental and theoretical investigation. Compared to ferroelectric semiconductors, the recently reported 2D metal ferroelectrics contribute to the performance of FTJs due to their excellent conductivity and low resistivity. This material increases the tunneling electroresistance (TER) and reduces the resistance-area (RA) for more efficient current transfer. In this work, we systematically investigate the electronic transport properties of the bilayer metal ferroelectric Nb₂NF₂ (2L-Nb₂NF₂)-based devices using first-principles calculations and the nonequilibrium Green’s function method. We found that the TER of Au/2L-Nb₂NF₂/Au at zero bias can be 1 order of magnitude higher than that of the reported bilayer semiconducting ferroelectric In₂Se₃ while exhibiting a 2 orders of magnitude lower RA of 0.05 Ω μm². The improved performance is attributed to the high electrical conductivity of 2L-Nb₂NF₂ and its contact with the metal to achieve a ferroelectric–antiferroelectric phase transition. These studies demonstrate the potential of metallic ferroelectrics and the metal-contact effect in transport in the field of nanoscale nonvolatile ferroelectric memory.