Highly Operable Ferroelectric Tunnel Junctions via Domain-Engineered Ferroelectrics and Interfacial Oxide Control

Ferroelectric tunnel junctions (FTJs) enable nondestructive readout using an ultrathin ferroelectric tunneling barrier, offering excellent scalability and ultralow switching energy for nonvolatile memory or in-memory computing. However, their practical implementation remains hindered by the rapid degradation of tunneling electroresistance (TER) during repeated cycling, which is often accelerated by grain boundary-assisted leakage and oxygen vacancy (V o )-induced interfacial degradation in ultrathin HfO 2 -based ferroelectrics. Here, we simultaneously improve TER and endurance in Hf 0.5 Zr 0.5 O 2 (HZO)-based FTJs by combining an oxide bottom electrode with an oxide interfacial layer at the top electrode to enable domain engineering and provide an oxygen reservoir. An Nb-doped SrTiO 3 (NSTO) [001] bottom electrode promotes a large-grained HZO microstructure, strengthening polarization-controlled tunneling. In addition, a Co top electrode spontaneously forms a CoO x interlayer that serves as an efficient oxygen exchange pathway, suppressing asymmetric V o accumulation during cycling. The resulting Au/Co/HZO/NSTO FTJ exhibits a giant TER of ≈ 1.36 × 10 7 and a large read margin, maintaining stable switching up to10 6 cycles with a read window on the order of 10 4 . These results highlight the synergistic roles of ferroelectric domain control and interfacial oxygen vacancy regulation, offering a viable route toward scalable and reliable ferroelectric tunneling devices based on ultrathin HZO.