Artificial Synapse Based on Back-Gated MoS₂ Field-Effect Transistor with High-k Ta₂O₅ Dielectrics

Herein, a multilayer MoS₂-based low-power synaptic transistor using Ta₂O₅ as a back-gate dielectric for mimicking the biological neuronal synapse is reported. The use of high-k dielectric allows for a lower-voltage swing compared with using conventional SiO₂, thus offering an attractive route to low-power synaptic device architectures. Exfoliated MoS₂ is utilized as the channel material, and the hysteresis in the transfer characteristics of the transistor is exploited to demonstrate excitatory and inhibitory postsynaptic currents, long-term potentiation, and long-term depression (LTP/LTD), indirect spike timing-dependent plasticity (STDP) based on single and sequential gate (V_g) pulses, respectively. The synapse had achieved a 35% weight change in channel conductance within 15 electrical pulses for negative synaptic gate pulse and 28% change for positive synaptic gate pulse. A complete tunability of weight in the synapse by spike amplitude-dependent plasticity (SADP) at a low voltage of 4 V is also demonstrated.