Artificial Synapse Based on van der Waals Heterostructures with Tunable Synaptic Functions for Neuromorphic Computing

Abstract

Two-dimensional (2D) materials and van der Waals heterostructures have attracted tremendous attention because of their appealing electronic, mechanical, and optoelectronic properties, which offer the possibility to extend the range of functionalities for diverse potential applications. Here, we fabricate a novel multiterminal device with dual-gate based on 2D material van der Waals heterostructures. Such a multiterminal device exhibited excellent nonvolatile multilevel resistance switching performance controlled by the source–drain voltage and back-gate voltage. Based on these features, heterosynaptic plasticity, in which the synaptic weight can be tuned by another modulatory interneuron, has been mimicked. A tunable analogue weight update (both on/off ratio and update nonlinearity) of synapse with high speed (50 ns) and low energy (∼7.3 fJ) programming has been achieved. These results demonstrate the great potential of the artificial synapse based on van der Waals heterostructures for neuromorphic computing.

Graphene memristive synapses for high precision neuromorphic computing

“…states. This tuning of weight values through the application of a separate bias could be considered reminiscent of heterosynaptic plasticity in biological neural networks, in which the stimulation of a given neuron causes a change in the strength (weight) of synaptic connections between other, inactivated, neurons 51,52 . The most well-known example of this mechanism is the existence of modulatory neurons, also known as interneurons.…”

“…In addition, repeated heterosynaptic modulation has, through study, been found to promote the growth/retraction of synaptic connections, creating persistent changes in synaptic weight and contributing to long-term memory formation/ storage 54 . This has made the implementation of heterosynaptic plasticity an important goal for developing the next generation of novel neuromorphic systems 52 . The modulation of conductance states afforded by different modulatory bias, V mod (V BG ), values can be seen in Supplementary Note 7.…”

Two-Dimensional Near-Atom-Thickness Materials for Emerging Neuromorphic Devices and Applications

“… (H) Biological synapse schematic with a modulatory input required for implementing heteroplasticity. Reprinted with permission from ( He et al., 2020 ). Copyright 2020 American Chemical Society.…”

“…For heterosynaptic plasticity, synaptic devices are required to be in three-terminal geometries, which are more suitable for accommodating the LTP with multiple synapses to maintain strong and efficient synaptic association, demanded in various applications such as sound localization ( Das et al., 2019 ; Sun et al., 2018 ). In the three-terminal devices that emulate heterosynaptic plasticity, the third input is utilized as the modulatory one ( Figure 6 H) as realized in FETs, which can be used as logic gates by emulating a biological process of dendritic integration ( He et al., 2020 ).…”

“…Energy consumption was further decreased in a MoS 2 FET using a graphene floating gate ( Paul et al., 2019 ), which demonstrated STDP with a remarkable endurance of 10 5 cycles and energy dissipation of ∼5 fJ. Recently, it was reported that a dual-gated MoS 2 FET exhibited tunable synaptic plasticity and high linearity of NLF = 0.5 during potentiation with identical input pulses ( He et al., 2020 ). Along with the results employing exfoliated 2D materials, CVD-grown MoS 2 was also exploited in achieving a six-terminal memtransistor.…”