Zinc oxide and indium-gallium-zinc-oxide bi-layer synaptic device with highly linear long-term potentiation and depression characteristics

Abstract

The electrical properties, resistive switching behavior, and long-term potentiation/depression (LTP/LTD) in a single indium-gallium-zinc-oxide (IGZO) and bi-layer IGZO/ZnO (ZnO: zinc oxide) memristors were investigated for synapse application. The use of the oxide bi-layer memristors, in particular, improved electrical properties such as stability, memristor reliability, and an increase in synaptic weight states. The set voltage of bi-layer IGZO/ZnO memristors was 0.9 V, and the reset voltage was around − 0.7 V, resulting in a low-operating voltage for neuromorphic systems. The oxygen vacancies in the X-ray photoelectron spectroscopy analysis played a role in the modulation of the high-resistance state (HRS) (oxygen-deficient) and the low-resistance state (oxygen-rich) region. The VRESET of the bi-layer IGZO/ZnO memristors was lower than that of a single IGZO, which implied that oxygen-vacancy filaments could be easily ruptured due to the higher oxygen vacancy peak HRS layer. The nonlinearity of the LTP and LTD characteristics in a bi-layer IGZO/ZnO memristor was 6.77% and 11.49%, respectively, compared to those of 20.03% and 51.1% in a single IGZO memristor, respectively. Therefore, the extra ZnO layer in the bi-layer memristor with IGZO was potentially significant and essential to achieve a small set voltage and a reset voltage, and the switching behavior to form the conductive path.

Interface Engineering Enables Multilevel Resistive Switching in Ultra-Low-Power Chemobrionic Copper Silicate

“…This functionality is crucial for implementing artificial neural networks capable of learning, memory storage, and pattern recognition, aligning with the principles of neuromorphic computing. 46 Accomplishing P&D by applying 40 consecutive pulses for potentiation and depression with pulse width and interval of 0.5 and 0.1 ms, respectively, completes this sentence! (Figure 5d).…”

Interface roughness effects and relaxation dynamics of an amorphous semiconductor oxide-based analog resistance switching memory

“…However, the oxygen vacancies in the active oxide layer as well as the active layer–electrode interface are also found to be leading to resistive switching. 26,54,57 The current–voltage characteristics of most a-IGZO-based memristors can be majorly associated with ohmic conduction ( I ≈ aV ), space-charge-limited current conduction (SCLC) ( I ≈ aV + bV 2 ), Child's square law region ( I ≈ cV 2 ), trap-assisted (filled/unfilled) conduction/tunnelling (TAT), Poole–Frenkel emission (PF) (ln( I / V ) ∝ V 1/2 ), Fowler–Nordheim tunnelling (FN) (ln( I / V 2 ) ∝ V −1 ), the thermionic emission model (ln( I ∝ √ V )), 14,15,18,20,21,27,49,54,57 and many more.…”

“…20,26,53 In our devices, a thin AlO x layer is present in between the bottom Al electrode and the a-IGZO active layer, which could act as a Schottky barrier and get modulated during the application of voltage bias. The effect of the interface layer during switching has been tested using the thermionic emission model, 14,15,18,20,21,27,49,54,57 which can be simply performed by plotting ln( I ) against V 0.5 . Fig.…”

“…The nature of the resistive switching in a-IGZO-based memristors could be effectively tuned by the choice of electrodes, varying layer thicknesses, elemental stoichiometry of the a-IGZO, parametric variation of a-IGZO deposition conditions, proximity of an additional layer, thermal effects, etc . 16–25 Earlier work in the literature on Al/a-IGZO/Al memristor devices reported analog/gradual resistive switching (GRS) with negative SET and positive RESET bias conditions. 26 More recently, abrupt/filament-type switching (ARS) with positive SET and negative RESET bias conditions has been reported in contrast to the previous studies.…”

Gradual conductance modulation by defect reorganization in amorphous oxide memristors

“…Therefore, amorphous oxides represented by amorphous InGaZnO (a-IGZO), which have adjustable non-stoichiometric components, excellent large-area deposition uniformity, low cost, low fabrication temperature, and multifunctional capabilities, are used in memristor fabrication to obtain suitable intrinsic properties and keep the device structure simple as well. 30–33 Recently, all-optical modulated synaptic behavior in a-IGZO devices has also been reported. 34 Other amorphous oxides also exhibit promising memristive properties, such as ZnSnO-based amorphous oxides, 35–39 a-SrVO x , 40 a-InWZnO, 41 a-InSnZnO, 42 etc.…”