Giant Tunneling Electroresistance with Low Resistance-Area\nin Bilayer Nb<sub>2</sub>NF<sub>2</sub> Nanosheet Ferroelectric Tunnel\nJunctions

Conventional\nvan der Waals ferroelectric tunnel junctions (FTJs),\nconsisting of a two-dimensional (2D) semiconducting ferroelectric\ntunneling barrier, have undergone extensive experimental and theoretical\ninvestigation. Compared to ferroelectric semiconductors, the recently\nreported 2D metal ferroelectrics contribute to the performance of\nFTJs due to their excellent conductivity and low resistivity. This\nmaterial increases the tunneling electroresistance (TER) and reduces\nthe resistance-area (RA) for more efficient current transfer. In this\nwork, we systematically investigate the electronic transport properties\nof the bilayer metal ferroelectric Nb<sub>2</sub>NF<sub>2</sub> (2L-Nb<sub>2</sub>NF<sub>2</sub>)-based devices using first-principles calculations\nand the nonequilibrium Green’s function method. We found that\nthe TER of Au/2L-Nb<sub>2</sub>NF<sub>2</sub>/Au at zero bias can\nbe 1 order of magnitude higher than that of the reported bilayer semiconducting\nferroelectric In<sub>2</sub>Se<sub>3</sub> while exhibiting a 2 orders\nof magnitude lower RA of 0.05 Ω μm<sup>2</sup>. The improved\nperformance is attributed to the high electrical conductivity of 2L-Nb<sub>2</sub>NF<sub>2</sub> and its contact with the metal to achieve a\nferroelectric–antiferroelectric phase transition. These studies\ndemonstrate the potential of metallic ferroelectrics and the metal-contact\neffect in transport in the field of nanoscale nonvolatile ferroelectric\nmemory.