“…Recently, a bio-inspired neuromorphic system based on a spiking neural network (SNN) has been widely investigated because of its power-efficiency and parallel signal processing properties [2][3][4][5]. With regard to its application, the neuromorphic system, which is a hardware implementation of an artificial neural network, has been utilized mostly for pattern recognition [6][7][8][9][10], but also as a denoising auto encoder [11], for color image reconstruction [12], and for speech recognition [13]. In addition, various kinds of electronic devices have been studied as an artificial synaptic device, a crucial building block for constructing neuromorphic systems, including resistive switching materials [14][15][16][17], phase change materials [18][19][20], ferroelectric materials [21,22], and transistors [23][24][25].…”