Artificial Synapse Emulated through Fully Aqueous Solution-Processed Low-Voltage In₂O₃ Thin-Film Transistor with Gd₂O₃ Solid Electrolyte

Abstract

Brain-like neuromorphic computing system provides an alternative approach for the future computer for its characteristics of high-efficiency, power-efficient, self-learning, and parallel computing. Therefore, the imitation of synapse behavior based on microelectronics is particularly important. Recently, the synaptic transistors have received widespread attention. Among them, solid oxide-based synaptic transistors are more compatible with the largescale fabrication than the liquid and organic-based transistors. So the development of oxide synaptic transistor is required. Here, a novel aqueous solution-processed Gd 2 O 3 is suggested to be the solid electrolyte for synaptic transistors. The microstructure and the dielectric properties of Gd 2 O 3 film are investigated, which show the potential for the simulation of synaptic transmission. Then, the fully aqueous solution-processed In 2 O 3 /Gd 2 O 3 thin-film transistor (TFT) is fabricated. The device exhibits an acceptable electrical performance with a small threshold voltage of 1.24 V, and a small subthreshold swing of 0.12 V/decade. The artificial synapse behavior is stimulated and the short-term plasticity of In 2 O 3 /Gd 2 O 3 TFT is studied. The dependence of its excitatory postsynaptic current on presynaptic pulse magnitude, width, and frequency is verified. Besides, the synapse behavior of devices under continuous illumination stresses is investigated. The lights with different photon energy have different effects on the synaptic transmission, which is related to the ionization of oxygen vacancies. Our results demonstrate that fully aqueous solution-processed In 2 O 3 TFT with Gd 2 O 3 solid electrolyte is a candidate for the synaptic transistor.

Synaptic transistors with aluminum oxide dielectrics enabling full audio frequency range signal processing

“…Synaptic behavior in the transistors have been demonstrated so far with different classes of gate dielectric materials and device architectures, such as floating gate 3 , metal oxide dielectrics 4 – 6 electrolyte insulators 7 , ionic liquids 8 , proton conductors 9 , and ferroelectric materials 10 . Among these approaches, electrolyte gating and ionic liquids promise ultra-low voltage (< 1 V) operation.…”

“…Metal oxide dielectrics, per their processing, can possess charge-trapping behavior 4 , 5 or can be implemented in floating gate mechanisms 18 , thereby providing memory behavior. These solid-state materials can be deposited at low processing temperatures via vacuum-based deposition methods 4 , 14 , as well as low-cost solution-based methods 5 , 6 . If the synaptic operation is enabled for a wide range of operation frequencies, metal oxide dielectrics can fill the gap between the electrolyte gated synaptic devices and ferroelectric transistors in future applications of bio-inspired electronics.…”

“…If the synaptic operation is enabled for a wide range of operation frequencies, metal oxide dielectrics can fill the gap between the electrolyte gated synaptic devices and ferroelectric transistors in future applications of bio-inspired electronics. Metal oxide dielectrics in synaptic transistors such as AlO x and Gd 2 O 3 6 have been produced by atomic layer deposition 4 or spin coating 5 , 6 with subsequent lithographical patterning of the deposited layers, so far 4 – 6 and their synaptic operation frequency have been demonstrated up to 500 Hz. Printing offers an advantage of avoiding lithographic patterning of the layers, which is desirable for roll-to-roll manufacturing of low-cost electronic devices and circuits.…”

Artificial Indium‐Tin‐Oxide Synaptic Transistor by Inkjet Printing Using Solution‐Processed ZrOx Gate Dielectric

“…[ 24 ] In contrast, Zhang and co‐workers reported in 2020, the synaptic In 2 O 3 TFT as a channel layer with Gd 2 O 3 as a EDL by solution process. [ 25 ] Also, Liang et al reported synaptic In 2 O 3 TFT based on solution‐processed Al 2 O 3 as a EDL. [ 26 ] To make fully solution‐processed synaptic transistor is still challenging.…”

“…[ 26 ] To make fully solution‐processed synaptic transistor is still challenging. The high‐k material such as AlO x , [ 26 ] TaO x , [ 27,28 ] HfO x , [ 29,30 ] and GdO x [ 25 ] are studied as a candidate for the gate dielectric of synaptic transistor.…”