Electron Transport in Ferroelectric Tunnel Junctions Based on Two-Dimensional Janus GeS Bilayers

The two-dimensional van der Waals (2D vdW) Janus materials have different atomic species on both sides to ensure their structural asymmetry and inherent out-of-plane polarizations. A novel 2D vdW Janus material, GeS, was found to develop ferroelectric tunnel junctions (FTJs) with low energy consumption and high response speed. Based on our first principles calculations, it is found that the Janus GeS bilayers own three stacking modes, and their lateral sliding and vertical displacement can both modulate the electron transport in GeS bilayer-based tunnel junctions. In addition, the FTJ based on GeGe-contacting GeS bilayer exhibits the highest on/off ratio. Our study expands the concept of sliding ferroelectricity to a new class of 2D vdW Janus materials and reveals the possible resistance switching mechanism of these materials in real devices. Furthermore, it provides theoretical guidance for the design of low-energy-consumption and fast-switching nanodevices based on 2D vdW Janus materials.