Anisotropic resistive switching of 2D-layered single crystal halide perovskite CsPb₂Br₅-based memristor

Metal halide perovskites (MHPs) have attracted attention in advanced memory technology, such as resistive switching (RS) devices, owing to their hysteretic behavior. However, the mechanisms underlying MHP-based RS devices remain elusive. We present a 2D-layered single-crystal (SC) CsPb₂Br₅ microsheet-based RS device with vertical and planar structures. Although RS occurs in both structural devices, the planar structured device exhibits volatile RS operation, whereas the vertically structured device exhibits bipolar RS characteristics, including a long retention time (> 2.5×10⁴ s), large on/off ratio (up to 10⁸), low-operating voltage (V_set < 0.32 V), and reset voltage-driven multilevel properties with a large resistance ratio (~ 10²) between each state. A possible RS mechanism of the vertically structured devices can be explained by the migration of active metal ions. The two-dimensional (2D)-layered structure induces partial localization of active metal elements between the Cs layers owing to its high migration barrier energy level along the [001] crystal direction. Experimental and theoretical analyses, including Auger electron spectroscopy depth-profile and density functional theory calculations support our suggestions. This work clarifies the operational mechanisms in SC MHP-based anisotropic RS and proposes the potential for SC MHP in advanced memory devices, marking a leap in the understanding and application of these materials for next-generation electronics.