Configurable NbO_x Memristors as Artificial Synapses or Neurons Achieved by Regulating the Forming Compliance Current for the Spiking Neural Network

For the first time, a configurable NbO_x memristor is achieved that can be configured as an artificial synapse or neuron after fabrication by controlling the forming compliance current (FCC). When the FCC ≤ 2 mA, the memristors exhibit the resistive-switching (RS) property, enabling multiple types of synaptic plasticity, including short-term potentiation, paired-pulse facilitation, short-term memory, and long-term memory. When the FCC ≥ 3 mA, the memristors can be electroformed and exhibit the threshold switching (TS) property with excellent endurance (>10¹²), thus achieving various biological neuron characteristics, such as threshold-triggering, strength-modulation of spike frequency, and leaky integrate-and-fire. This enables the successful implementation of a spiking Pavlov's dog that employs the spikes as information carrier by connecting an RS NbO_x memristor as artificial synapse and a TS memristor as artificial neuron in series. Furthermore, a fully NbO_x memristors-based single-layer spiking neural network is simulated. It is first found that, due to the forgetting property of synapse, the recognition accuracy for the Modified National Institute of Standards and Technology handwritten digits is increased from 85.49% to 91.45%. This study provides a solid foundation for the development of neuromorphic machines based on the principles of the human brain.