Artificial synaptic and self-rectifying properties of crystalline (Na1-K )NbO3 thin films grown on Sr2Nb3O10 nanosheet seed layers

Abstract

• Crystalline Na 1-x K x NbO 3 (CNKN) film grown on Sr 2 Nb 3 O 10 (SNO) seed layer at 370 °C. • CNKN film grown on one SNO monolayer shows typical bipolar switching properties. • CNKN film grown on two SNO monolayers shows self-rectifying switching properties. • The CNKN memristor with two SNO monolayers shows artificial synaptic properties. • The CNKN film can be used to fabricate ANNs with a cross-point array structure. Crystalline (Na 1- x K x )NbO 3 (NKN) thin films were deposited on Sr 2 Nb 3 O 10 /TiN/Si (S-TS) substrates at 370 °C. Sr 2 Nb 3 O 10 (SNO) nanosheets served as a template for the formation of crystalline NKN films at low temperatures. When the NKN film was deposited on one SNO monolayer, the NKN memristor exhibited normal bipolar switching characteristics, which could be attributed to the formation and destruction of oxygen vacancy filaments. Moreover, the NKN memristor with one SNO monolayer exhibited artificial synaptic properties. However, the NKN memristor deposited on two SNO monolayers exhibited self-rectifying bipolar switching properties, with the two SNO monolayers acting as tunneling barriers in the memristor. The conduction mechanism of the NKN memristor with two SNO monolayers in the high-resistance state is attributed to Schottky emission, direct tunneling, and Fowler–Nordheim (FN) tunneling. The current conduction in this memristor in the low-resistance state was governed by direct tunneling and FN tunneling. Additionally, the NKN memristor with two SNO monolayers exhibited large ON/OFF and rectification ratios and artificial synaptic properties. Therefore, an NKN memristor with two SNO monolayers can be used for fabricating artificial synaptic devices with a cross-point array structure.