Heterosynaptic Plasticity Achieved by Highly Anisotropic Ionic Migration in Layered Li_xMoO₃ for Neuromorphic Application

Abstract Heterosynaptic plasticity is important for the implementation of biological functions in an excitatory synapse. Although plenty of devices have been developed to emulate the synaptic behaviors, the capability of processing information with high heterosynaptic plasticity remains challenging. Herein, it is reported that the electrical conductance of Li⁺ ion pre‐intercalated MoO₃ nanosheet (Li_xMoO₃: 0 < x < 1) can be efficiently modulated, relying on the local phase transition associated with electric‐field‐driven ionic migration. The Li_xMoO₃‐based in‐plane synaptic device exhibits attractive nonvolatile memory performance including high switching ratio (≈500) and long‐term retention of states (>4000 s). By combining experimental studies with theoretical calculations, the anisotropic in‐plane ionic migration in Li_xMoO₃ is revealed, which is attributed to the dissimilarity of adiabatic barriers along different crystallographic directions. A multiterminal Li_xMoO₃ memristor responses anisotropically to input spikes, and the slope of conductance change along a‐axis is almost 7 times larger than that along c‐axis, which contributes to the emulation of heterosynaptic plasticity required for neurobiological architecture. Additionally, the device can also fulfill the in‐memory Boolean logic operations naturally. This work demonstrates the great potentials of ionic migration to develop artificial synapses, highlighting its promising applications for future brain‐inspired computing systems.