Vortex Topology Enables Biomimetic Synaptic Plasticity in Lead-Free KNN Ferroelectric Thin Films: Insights from...

Multilevel memristors based on perovskite are promising candidates for high-density storage, and controllable vortex topologies have significant application potential in biomimetic synapses. However, realizing complete and efficient biological synaptic functions that combine memory and computation remains a long-standing challenge. In this paper, by matching synaptic plasticity electric field design, seven types of biological synaptic neuron functions are fully realized for the first time through vortex structures in the potassium sodium niobate thin films. Through the analysis of the phase-field method, it is demonstrated that the domain pattern transformation realized by different functions mainly comes from the energy competition between ferroelastic twin domain walls and different electric field pulses. By analyzing the enhanced signal positions from two opposite sources, it is found for the first time that the ferroelastic twin domain structure simultaneously causes two polarization variants in opposite out-of-plane directions. Based on more than 100 functional regions, under the applied electric field of 0.01 V nm^-1, the realized paired pulse facilitation function has a signal enhancement up to 16 times relative to traditional transistors. Both spiking-timing-dependent plasticity and spiking-rate-dependent plasticity achieve exceeding 80% pulse signal recognition performance. This will promote the realization of easily integrated independent biological synaptic neurons in bionics.