2019

Tan, Hongwei; Bhattacharya, Sayani; Qin, QiHang; Lahtinen, Jouko; van Dijken, Sebastiaan

Activated by action potentials and Ca²⁺ ion migration, neurotransmitters in biological synapses are released from vesicles at the presynaptic membrane to the cleft and bonded to receptors on the postsynaptic membrane. The bonded neurotransmitters modify the electrochemical properties of the postsynaptic membrane and, thereby, the synaptic plasticity, which forms the basis for learning, memory, emotion, cognition, and consciousness. Here, the oxygen vacancy transport in Au/SrTiO₃ (STO)/La_0.67Sr_0.33MnO₃ (LSMO) tunnel junctions is exploited to mimic neurotransmission processes in an artificial ionic electronic device. Using voltage pulses of varying number, amplitude, and polarity, it is demonstrated that reversible oxygen vacancy migration across the STO/LSMO interface provides stable multilevel resistance switching for octal memory devices and resembles the quantal, stochastic, and excitatory or inhibitory nature of neurotransmitter release dynamics. Moreover, fundamental synaptic behaviors including long‐term potentiation/depression and various types of spike‐timing‐dependent plasticity characteristics are emulated, opening a promising biorealistic approach to the design of neuromorphic devices.