CMOS-compatible synaptic transistor gated by chitosan electrolyte-Ta2O5 hybrid electric double layer

Abstract

This study proposes a hybrid electric double layer (EDL) with complementary metal-oxide semiconductor (CMOS) process compatibility by stacking a chitosan electrolyte and a Ta2O5 high-k dielectric thin film. Bio-inspired synaptic transistors with excellent electrical stability were fabricated using the proposed hybrid EDL for the gate dielectric layer. The Ta2O5 high-k dielectric layer with high chemical resistance, thermal stability, and mechanical strength enables CMOS-compatible patterning processes on biocompatible organic polymer chitosan electrolytes. This technique achieved ion-conduction from the chitosan electrolyte to the In-Ga-Zn oxide (IGZO) channel layer. The on/off current ratio, subthreshold voltage swing, and the field-effect mobility of the fabricated IGZO EDL transistors (EDLTs) exhibited excellent electrical properties of 1.80 × 107, 96 mV/dec, and 3.73 cm2/V·s, respectively. A resistor-loaded inverter was constructed by connecting an IGZO EDLT with a load resistor (400 MΩ) in series. This demonstrated good inverter action and responded to the square-wave input signals. Synaptic behaviours such as the hysteresis window and excitatory post-synaptic current (EPSC) variations were evaluated for different DC gate voltage sweep ranges and different AC gate spike stimuli, respectively. Therefore, the proposed organic–inorganic hybrid EDL is expected to be useful for implementing an extremely compact neural architecture system.

Edible Dielectric Composite for the Enhancement of Performance and Electromechanical Stability of Eco-Friendly Flexible Organic Transistors

“…In addition, these dielectrics are not suitable for biodegradability. Significant contributions have been made by researchers through the development of entirely or partially biodegradable transistors using numerous edible or biopolymer dielectrics such as gelatin, cellulose, guanine, silk, adenine, chitosan, starch, dextran, and so forth. − However, considerable challenges still exist in the accomplishment of low voltage operated organic transistors with excellent electrical and operational endurance with these natural dielectric materials. ,, The use of pristine biopolymers generally results in low electromechanical stability in devices due to inherent polar hydrophilic functional groups in these biopolymers which cause the device to degrade rapidly . These hydrophilic groups can trap mobile charge carriers, constraining the performance with reduced drain current and induction of hysteresis .…”

“…Among various biopolymers, gelatin and chitosan are the most commonly explored materials as a gate dielectric in transistors. ,− Gelatin is easily soluble in water and forms complexes with other molecules because of the available functional groups acting as binding sites . This protein enables the formation of a smooth film with excellent dielectric properties for the development of low voltage operated devices. − Additionally, chitosan is a polysaccharide derived from chitin, containing amino polysaccharide molecules having a strong positive electrical charge, enabling it to bond very strongly with functional groups of gelatin. , It is widely explored in oxide-based synaptic transistors and capacitors due to its advantages of mechanical stability, transparency, high capacitance for protonic mobile ions, and temperature stability. ,, The incorporation of chitosan in composite reduces the elastic modulus of the gelatin film leading to increased elongation at break value indicating higher ductility for composite than the individual parent film . The formation of strong hydrogen bonding between the ammonium groups of chitosan and the negatively charged side-chain groups in gelatin forms polyelectrolyte complexes resulting in film strengthening.…”

“…49,50 It is widely explored in oxide-based synaptic transistors and capacitors due to its advantages of mechanical stability, transparency, high capacitance for protonic mobile ions, and temperature stability. 27,47,51 The incorporation of chitosan in composite reduces the elastic modulus of the gelatin film leading to increased elongation at break value indicating higher ductility for composite than the individual parent film. 52 The formation of strong hydrogen bonding between the ammonium groups of chitosan and the negatively charged side-chain groups in gelatin forms polyelectrolyte complexes resulting in film strengthening.…”

Threshold-Variation-Tolerant Coupling-Gate α-IGZO Synaptic Transistor for More Reliably Controllable Hardware Neuromorphic System

“…In this work, a novel synaptic device based on field-effect transistor (FET) operated by coupling gate, coupling-gate amorphous indium-gallium-zinc-oxide (α-IGZO), or shortly, CG-IGZO synaptic transistor is designed, fabricated, and characterized. Although there have been related research results on either FET-based or GZO-based synaptic devices recently [13], [14], in this work, a novel structuring with CG is regarded as a distinctive aspect in designing a synaptic transistor. By introducing the peculiar gate structuring, the synaptic weight can be more discriminatively tuned in the highly reproducible and practical ways of both fabrication and layout design.…”

Sol-Gel Composites-Based Flexible and Transparent Amorphous Indium Gallium Zinc Oxide Thin-Film Synaptic Transistors for Wearable Intelligent Electronics

“…To solve these problems, recent studies have focused on the hybridization of organic and inorganic materials. In particular, Ta 2 O 5 is a biocompatible high-k material, and when used as a barrier to the chitosan EDL layer, it stabilizes the chemical resistance and improves the mechanical strength, allowing compatibility with the CMOS process of the chitosan layer [ 13 , 14 , 15 ]. Meanwhile, the rapid advancement of display technology has accelerated the popularization of transparent and flexible electronic devices, which are expected to fulfill future technological requirements that are difficult to achieve with silicon-based electronic devices [ 16 ].…”