Improved Resistive Switching with Low-Power Synaptic Behaviors of ZnO/Al2O3 Bilayer Structure

Abstract

In this work, the resistive switching behavior of bilayer ZnO/Al2O3-based resistive-switching random access memory (RRAM) devices is demonstrated. The polycrystalline nature of the ZnO layer confirms the grain boundary, which helps easy oxygen ion diffusion. Multilevel resistance states were modulated under DC bias by varying the current compliance from 0.1 mA to 0.8 mA, the SET operations where the low resistance state of the memristor device was reduced from 25 kΩ to 2.4 kΩ. The presence of Al2O3 acts as a redox layer and facilitates oxygen vacancy exchange that demonstrates stable gradual conductance change. Stepwise disruption of conductive filaments was monitored depending on the slow DC voltage sweep rate. This is attributed to the atomic scale modulation of oxygen vacancies with four distinct reproducible quantized conductance states, which shows multilevel data storage capability. Moreover, several crucial synaptic properties such as potentiation/depression under identical presynaptic pulses and the spike-rate-dependent plasticity were implemented on ITO/ZnO/Al2O3/TaN memristor. The postsynaptic current change was monitored defining the long-term potentiation by increasing the presynaptic stimulus frequency from 5 Hz to 100 Hz. Moreover, the repetitive pulse voltage stimulation transformed the short-term plasticity to long-term plasticity during spike-number-dependent plasticity.

Analog Memory and Synaptic Plasticity in an InGaZnO-Based Memristor by Modifying Intrinsic Oxygen Vacancies

“…Improvement of multilevel memory state and gradual resistive switching have been reported in the context of a bilayer-based structure involving binary oxides and InGaZnO. In this setup, control over CFs was achieved at the interface, which led to more dependable resistive switching characteristics [9,[12][13][14][15]. The proper introduction of metal ion doping in InGaZnO has also shown a high On/Off ratio along with enhanced resistive switching properties [11].…”

Long‐ and Short‐Term Memory Characteristics Controlled by Electrical and Optical Stimulations in InZnO‐Based Synaptic Device for Reservoir Computing

“…The stable switching characteristics achieved by incorporating a thin Al 2 O 3 layer have been extensively documented in prior research. [53,54] Unlike the ITO/IZO/TaN single-layer device, the addition of a thin Al 2 O 3 layer in the bilayer device enhances the stability of the improves the inherently irregular switching properties. This phenomenon can be attributed to the formation and rupture of filaments at the IZO/Al 2 O 3 interface and the creation of virtual electrodes within IZO.…”

Improved Uniformity of TaOx-Based Resistive Switching Memory Device by Inserting Thin SiO2 Layer for Neuromorphic System

“…The cycle-to-cycle and device-to-device are critical considerations in evaluating RRAM devices since the RS phenomenon of oxide materials occurs as a result of the development and rupture of conductive filaments created by the migration of randomly distributed defects [ 29 , 30 , 31 ]. Several methods exist to improve filamentary uniformity: ion doping [ 32 ], bilayer structure [ 33 ], and defective circuit breakers [ 34 ]. Many reports on bilayer structures have been conducted because of their efficient and simply executable ways of generating stable and controllable resistive switching behavior [ 35 , 36 , 37 ].…”