Multiple connected artificial synapses based on electromigrated Au nanogaps

Abstract

Building an artificial synaptic device with multiple presynaptic inputs will be a significant step toward realization of sophisticated brain-inspired platforms for neuromorphic computing. However, an artificial synapse that can mimic functions of multiple synapses in a single device has not yet been well developed with existing electronic devices. Here, we experimentally implement the functions of multiple synapses in a single artificial synaptic device consisting of multiple connected nanogap electrodes. The “activation” technique, which is based on electromigration of metal atoms induced by a field emission current, was applied to the device to emulate the synaptic functions. We show that the device, upon application of activation, exhibits conductance changes in response to stimulation voltage, similar to the memory states of biological synapses. Several important synaptic responses—notably, short-term plasticity and long-term plasticity—were successfully demonstrated in multiple connected Au-nanogaps. For further application, a simple network was implemented using multi-input devices based on a two-terminal Au nanogap array, exhibiting the ability to classify the digital input vector pattern. These demonstrations pave the way for brain-inspired computing applications such as associative memory, pattern classification, and image recognition.