Giant tunnel electroresistance in two-dimensional ferroelectric tunnel junctions constructed with a Sc2CO2/In2Se3 van der Waals ferroelectric heterostructure

Two-dimensional (2D) ferroelectric materials have attracted great attention in recent years due to their thin thickness, high stability, and switchable polarization states. In particular, ferroelectric tunnel junctions (FTJs) constructed from 2D ferroelectric materials have been shown to have very high tunnel electroresistance (TER) ratios. In this work, we design a ferroelectric tunnel junction composed of ${\mathrm{Sc}}_{2}{\mathrm{CO}}_{2}/{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ vertical van der Waals (vdW) heterostructure based on two different 2D ferroelectric materials with out-of-plane polarization. Through density functional calculations combined with a nonequilibrium Green's function technique, it is found that the TER ratio as high as ${10}^{7}%$ can be achieved. Analysis shows that it originates from the difference in the work functions of the contact surfaces of the two ferroelectric materials, which makes charge transfer occur or not occur between them and further leads to a metalinsulator switching of the ferroelectric vdW heterostructure upon the reversion of the applied electrical field. The results suggest the importance of ferroelectric vdW heterostructure in the design of FTJs and a feasible design scheme characterized by proper choice of the work functions and band gaps of the component materials.