Synaptic Properties of Geopolymer Memristors: Synaptic Plasticity, Spike-Rate-Dependent Plasticity, and Spike-Timing-Dependent Plasticity

Abstract

Memristors, also known as artificial synapses, are devices that are able to mimic the memory functions of biological synapses. To emulate synaptic functions, memristors need to exhibit plasticity, which is a pivotal phenomenon in their biological counterparts. In a previous work, we demonstrated that geopolymers present memristive properties. In this work, we study different types of synaptic plasticity properties of geopolymer memristors. We demonstrate short-term and long-term memory resulting from potentiation-depression; Hebbian learning inspired spike-timing-dependent plasticity, spike-rate-dependent plasticity, historydependent plasticity, paired-pulse facilitation, paired-pulse depression, and post-tetanic potentiation. These synaptic properties can be ascribed to the electro-osmosis-induced movement of ions in the capillaries and pores of the geopolymer memristors. These properties are extremely promising for the use of geopolymers in neuromorphic computing applications.

Recent progress of organic artificial synapses in biomimetic sensory neural systems

“…STDP changes synaptic weight according to the timing between the presynaptic and the postsynaptic action potential. 63 Typically, presynaptic spikes appear a few milliseconds before postsynaptic spikes, which increases synaptic weights. Conversely, a postsynaptic spike appears a few milliseconds before a presynaptic spike, which decreases the synaptic weight.…”

“…A high frequency (20–100 Hz) train of presynaptic spikes results in potentiation, whereas a low frequency (1–5 Hz) one leads to depression. 63…”

Synaptic Characteristics and Vector‐Matrix Multiplication Operation in Highly Uniform and Cost‐Effective Four‐Layer Vertical RRAM Array

“…[17,18] It is time to begin considering a possible path for the commercialization of RRAM, which has attracted much interest in research laboratories and the semiconductor industry over the past years. [19][20][21][22][23][24][25][26][27] Resistive switching memories of various materials are applicable in commercialization in two ways: 1) high-density memory with the likely architecture of a crossbar array or vertical NAND-like structure [17] ; and 2) new computing or memory unit, such as in neuromorphic computing or dynamic logic software. [18] These ideas may coincide with the "beyond-Moore" approach.…”

“…There are two ideal methods for designing high-density 3D structures: lateral and vertical scaling. [24,25] Lateral scaling, also known as "3D X-point RRAM," employs stacked X-point arrays with metal lines orthogonally crossing one another, and memory cells are produced where the lines cross on the plane. [5,6,14] The memory scaling barrier may also be solved through vertical scaling technologies alongside lateral scaling.…”