Fast Operations of Nonvolatile Ferroelectric Domain Wall Memory with Inhibited Space Charge Injection

The microampere-level domain wall currents in LiNbO₃ single crystals have promising applications in nonvolatile ferroelectric domain wall random access memory and logic with high-density integration, ultrafast operation speeds, and almost unlimited switching cycles. For the memory commercialization, the improvements of the reliability and operation speed of the devices are challenging due to the high-field charge injection. The injected charge could compensate the domain-wall boundary charge that screens the domain switching field and reduces the domain wall current. In this work, two kinds of memory nanocells were fabricated on the surfaces of X-cut LiNbO₃ single crystals to study the geometry-dependent charge injection. The striped memory cell due to the appearance of the size-driven reconstruction has a smaller coercive field than that of a clamped memory cell without relaxation of the lattice matching stress, which reduces low-frequency charge injection and increases the domain switching speed. At an operating voltage of 5 V, we observed a retention time of more than 1 week and an on/off current ratio of 2 × 10⁴ for a striped-like cell, paving the route to integrate energy-efficient high-density domain wall memory in high reliability.