Sliding Ferroelectric Tunnel Junctions with Ultrahigh Tunneling Electroresistance

Abstract

Sliding ferroelectricity in van der Waals materials offers an appealing route to compact, nonvolatile, atomically thin ferroelectric tunnel junctions (FTJs) with low switching energy, but achieving a large resistance contrast in such devices remains challenging because the weak out-of-plane polarization provides limited electrostatic modulation of the tunneling barrier. Here, using bilayer rhombohedral MoS2 as a sliding ferroelectric barrier, we demonstrate room-temperature sliding FTJs with tunneling electroresistance (TER) values exceeding 3.2 × 105. We show that this giant contrast arises from a height–width hybrid tunneling mechanism, in which polarization reversal simultaneously modulates the tunnel barrier height and switches a nanoscale interfacial depletion width, yielding exponential amplification of the tunneling contrast. Spatially resolved tunneling, piezoresponse, and Raman measurements reveal that local strain, rather than ferroelectric domain walls, dominates spatial variations in the TER by modulating the sliding ferroelectric dipole strength, the OFF-state depletion width, and the resulting TER amplification. Finally, planar 3R-MoS2 FTJs further validate this mechanism by exhibiting a TER above 105, a switching energy density of several fJ μm–2, and projected endurance beyond 106. These results provide fundamental insight into the nanoscale electrostatics in sliding ferroelectric-based tunnel junctions while pointing toward low-energy, high-contrast nonvolatile memory applications.