Ion Crowding Effect in Unilaterally Downsized Perovskite Memristors

Minimizing the footprint of individual cells in a memristor array is crucial for increasing packing density, reducing power consumption and boosting computational performance. However, the downscaling of memristive devices incorporating halide perovskites has been challenging due to the polycrystalline nature of the active layer. In this work, we employed monocrystalline nanoplates of the all-inorganic perovskite CsPbBr₃, and combined nanofabrication and conductive atomic force microscopy to progressively downsize the memristors to the micrometer and nanometer scale. We report an ion crowding effect in these micro- and nano- devices with unilaterally downscaled electrodes. The ion crowding effect is analogous to the current crowding effect in bipolar junction transistors, and originates from the substantially enhanced electric field in the peripheral of downsized electrodes. This effect fundamentally alters the microscopic ionic transport and distribution, leading to distinct switching behaviors and morphological deformation including protrusions and indentations. Further downsizing the critical dimension of memristors to 30 nm intensifies the crowding effect, resulting in anisotropic switching characteristics and unique "hole-in-a-bump" surface feature. This study offers insight into the field-induced ionic behaviors at microscale, and lays the groundwork for miniaturized perovskite memristors.