Oxide-based Electric-double-layer Thin-film-transistors And Their Applications In Artificial Synapses

Iontronics is a newly emerging interdisciplinary concept which bridges electronics and ionics,covering electrochemistry,solid-state physics,electronics and biological science.In iontronics,the emphasis is given on the interaction between electrons and ions or the modulation of ions on electrons.Electrolyte gating is one of the typical techniques in iontronics.It enables realization of new concept devices with functions,such as field-induced superconductivity,ferromagnetism and Mott transition.Electric-double-layer transistors?EDLTs? are typical iontronic devices.EDLTs employ ion-conducting electrolyte films as gate dielectric.Due to the unique ion-gating behavior,EDLTs are very suitable for synaptic device.In this thesis,oxide-based electric-double-layer thin-film-transistors were fabricated.Different operation modes were demonstrated.And several important synaptic behaviors were mimicked.The main contents of this work can be summarized as follows:?1?Phosphorus silicon glass nanogranular?PSG?electrolyte films were deposited by plasma enhanced chemical vapor deposition.High proton-conductivity of⁹×10^-4S/cm and high electric-double-layer capacitance of⁵?F/cm² were observed for the films at room temperature.Taking this PSG electrolyte film as the gate dielectric,oxide electric-double-layer thin-film-transistors were prepared by using low-cost process.The fabricated devices showed good electric performance with both bottom-gate and coplanar-gate.Taking self-assembled ITO EDLT for an example,the operation voltage and the subthreshold swing was as low as 1.5V and 80mV/dec,respectively.The mobility and the current on/off ratio was as high as 7 cm²V^-1s^-1 and1×10⁷,respectively.?2?A pseudo-diode operation mode was demonstrated on the fabricated IGZO EDLTs.With the modulating voltage altered from-0.9V to 0.1V,the current rectification ratio of the pseudo-diode increased from² to⁵0000.And also,important inhibitory synaptic behaviors were successfully mimicked on the pseudo-diode,such as hyperpolarization/deporlarization of post-synaptic current,short-term-depression behavior and adaptation behavior.?3?Compared with traditional thermally-oxidized SiO₂ based capacitor,short-term decaying behavior was discovered in PSG electrolyte based capacitor upon charging current.This slow-decayed discharging behavior could be attributed to the unique ion-gating behavior.On this basis,a dual-coplanar gate operation mode was designed.It was proposed for Hodgkin-Huxley Artificial Synaptic Membrane.Several membrane potential behaviors were successfully mimicked,such as resting potential,excitatory/inhibitory post-synaptic potential,membrane depolarization/hyperpolarization and acttion potential.