Energy-efficient synaptic devices based on planar structured h-BN memristor

Synapses with short-term plasticity (STP) and long-term plasticity (LTP) behaviors are the key factors for the development of complex neuromorphological systems. Two dimensional (2D) materials have shown great potential at synaptic devices because of their unique properties. In this work, synaptic devices with a planar structure using insulated 2D hexagonal boron nitride (h-BN) as resistance switching (RS) medium were studied for the first time. Different from vertical h-BN synaptic devices, planar h-BN synaptic devices support in-plane transport of metal ions through nanoscale channels, which weakens the influence of material defects, morphology, thickness and uniformity on device performance. The Ag/h-BN/Ag planar structured synaptic devices exhibited low switching voltage (< 1 V), high On/Off ratio (> 108), wide range of tunable operation current (0.1 nA–1 mA), and coexistence of volatile (SET power ≤ 50 nW) and non-volatile (SET power ≥ 700 nW) RS characteristic. In addition, the multi-stage resistance states could be modulated by setting different SET power. The device efficiently mimicked the STP and LTP synaptic functions, and the energy consumption per synaptic event was as low as 170 fJ/spike for STP and 540 fJ/spike for LTP, respectively. In addition, the multi-memory states of synaptic devices could be obtained by adjusting the postsynaptic current (PSC).