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.
Highlights
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 arrows “1” and “2” in the figure are referred to as “SET,” and they indicate that the resistive switching (RS) behaviors of the single IGZO and bi-layer IGZO/ZnO memristors change from high-resistance state (HRS) to low-resistance state (LRS)
The process of changing from arrow “3” to “4” in the figure is called “RESET,” and it means that the RS behaviors of the single IGZO and bi-layer IGZO/ ZnO memristors change from LRS to HRS
Summary
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 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 potentiation and depression characteristics of single-layer memristor devices are frequently nonlinear, resulting in less efficient neural network processing. The use of oxide bi-layers improved electrical properties such as stability, memristor reliability, and an increase in synaptic weight s tates[26,27,28]. This paper proposed bi-layer IGZO/ZnO memristors to improve the electrical characteristics and synaptic linearity in long-term potentiation/depression (LTP/LTD) characteristics compared with a single IGZO memristor. The high linearity in LTP/ LTD characteristics of the bi-layer IGZO/ZnO memristors is more linear than that of other reported devices[29,30,31,32]
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