Neural synaptic functions of Pt/NSTO/In self-rectifying memristors with Schottky barriers

Memristors with self-rectifying properties are capable of suppressing sneak currents in crossbar arrays and become a key component for constructing artificial synapses. Their performance usually depends on the formation of the interface barrier, so the regulation of the interface barrier on the synaptic functions will be investigated. In this study, Pt/NSTO/In self-rectifying memristors were fabricated based on 0.05 and 0.7 wt. % Nb doped SrTiO3 (NSTO) single crystals. The resistive switching behavior originates from the modulation of the Pt/NSTO Schottky barrier, and the barrier difference of Pt/0.7NSTO between the high-resistance state (HRS) and low-resistance state (LRS) is more pronounced due to the higher carrier concentration and larger interface trap density. For both Pt/NSTO/In memristors, continuous multistate conductance can be modulated by adjusting the applied pulse amplitude, interval, and width. Results on synaptic function simulation, such as paired-pulse facilitation, long-term potentiation/long-term depression, excitatory postsynaptic currents, habituation, and short-term memory-to-long-term memory transition, show that the Pt/0.7NSTO/In device exhibits superior conductance modulation precision, habituation–dishabituation behavior, and memory retention capability, which can be attributed to the higher Schottky barrier between HRS and LRS for Pt/0.7NSTO. So modulating the interface barrier can effectively optimize the synaptic behaviors of memristors, which provide valuable technical guidance for memristor optimization.