High readout domain-wall currents in LiNbO3 single-crystal nanodevices are attractive because of their application in a ferroelectric domain wall random access memory (DWRAM) to drive a fast memory circuit. However, the wall current at a small read voltage would increase nonlinearly at a much higher write voltage, which could cause high energy consumption. Here, we resolved this problem by controlling the two-step domain forward growth within a ferroelectric mesa-like cell that was formed at the surface of an X-cut LiNbO3 single crystal. The mesa-like cell contacts two side Pt/Ni electrodes that extend over the cell surface by 90 nm for the generation of an in-plane inhomogeneous electric field. The domain forward growth processes at first in the formation of an inclined charged 180° domain to span the in-plane electrode gap under a write voltage of 5 V in a large readout wall current, and then, the domain expands fully throughout the entire cell in the formation of a neutral 180° wall to reduce the wall current by 10 times at a higher write voltage of 6 V. Meantime, the domain below the mesa-like cell in an opposite orientation is unchanged to serve as the reference. A higher wall current at a lower read voltage and a lower wall current at a higher write voltage can satisfy both requirements of low energy consumption and fast operation speeds for the DWRAM.
Keywords: LiNbO3 single crystal; domain switching dynamics; domain wall current; energy-efficient memory; operation speed.