Resistive switching characteristics in memristors with Al2O3/TiO2 and TiO2/Al2O3 bilayers

We have investigated characteristics of Al2O3 thin films, which are deposited by plasma-enhanced atomic layer deposition (PE-ALD) and thermal ALD (TH-ALD) with oxygen plasma and H2O as oxidant gas, respectively, and Al(CH3)3 precursor. The Al2O3 film, which was deposited at 50℃, exhibited a large leakage current property. The positive (～10 18 cm-3) and negative fixed charges (～10 12 cm-2) occurred in Al2O3 film and at SiO2/Al2O3 interface by PE-ALD process at below 150℃, respectively. On the other hand, the opposite fixed charges were observed by TH-ALD process. This is due to the different reactive intermediates of Al-CO and Al-O-Al-CH groups in Al2O3 film by PE-ALD and TH-ALD processes, respectively. The fixed charge in Al2O3 film disappeared over 200℃. The dipole (～10 13 cm-2) also occurs at SiO2/Al2O3 interface and leads to positive flatband shift of 0.6 V. Therefore, we should pay careful attention to ALD condition such as oxidant gas and growth temperature considering to applications.

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Section: はじめにunclassified

Influence of Oxidant Gas of Atomic Layer Deposition on Electrical Characteristics of Al2O3 films

Nabatame¹,

Kimura

Yuge

et al. 2018

Vac. Surf. Sci.

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“…In all cases, the origin of switching has been attributed to either the drift of oxygen vacancies 28 and/or interstitials 29 or the formation of conductive filaments 30 within an active metal-oxide core under the influence of an applied electrical field. Within that context several studies have reported on the importance of interface interactions and properties 31 , showing that the introduction of a thin interfacial barrier layer between the active layer and one of the electrodes can influence the electrochemical processes, the devices’ stability 32 , 33 , improve its switching characteristics and reduce the overall power consumption 34 – 37 .…”

Section: Introductionmentioning

confidence: 99%

Multibit memory operation of metal-oxide bi-layer memristors

Stathopoulos

Khiat

Trapatseli

et al. 2017

Sci Rep

268

202

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Emerging nanoionic memristive devices are considered as the memory technology of the future and have been winning a great deal of attention due to their ability to perform fast and at the expense of low-power and -space requirements. Their full potential is envisioned that can be fulfilled through their capacity to store multiple memory states per cell, which however has been constrained so far by issues affecting the long-term stability of independent states. Here, we introduce and evaluate a multitude of metal-oxide bi-layers and demonstrate the benefits from increased memory stability via multibit memory operation. We propose a programming methodology that allows for operating metal-oxide memristive devices as multibit memory elements with highly packed yet clearly discernible memory states. These states were found to correlate with the transport properties of the introduced barrier layers. We are demonstrating memory cells with up to 6.5 bits of information storage as well as excellent retention and power consumption performance. This paves the way for neuromorphic and non-volatile memory applications.

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“…Recently, we developed an approach to design thin-film TiO 2 /Al 2 O 3 bilayer structures [14,15], exhibiting electric-field analog tuning of the nonvolatile resistance state in the range of seven orders of magnitude. Despite a wide memory window and the existence of multiple nonvolatile resistance states, TiO 2 /Al 2 O 3 bilayer structures demonstrate nonlinear behavior originating from the initial difference in the resistive properties of TiO 2 and Al 2 O 3 layers.…”

Section: Introductionmentioning

confidence: 99%

Contact Engineering Approach to Improve the Linearity of Multilevel Memristive Devices

et al. 2021

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Physical mechanisms underlying the multilevel resistive tuning over seven orders of magnitude in structures based on TiO2/Al2O3 bilayers, sandwiched between platinum electrodes, are responsible for the nonlinear dependence of the conductivity of intermediate resistance states on the writing voltage. To improve the linearity of the electric-field resistance tuning, we apply a contact engineering approach. For this purpose, platinum top electrodes were replaced with aluminum and copper ones to induce the oxygen-related electrochemical reactions at the interface with the Al2O3 switching layer of the structures. Based on experimental results, it was found that electrode material substitution provokes modification of the physical mechanism behind the resistive switching in TiO2/Al2O3 bilayers. In the case of aluminum electrodes, a memory window has been narrowed down to three orders of magnitude, while the linearity of resistance tuning was improved. For copper electrodes, a combination of effects related to metal ion diffusion with oxygen vacancies driven resistive switching was responsible for a rapid relaxation of intermediate resistance states in TiO2/Al2O3 bilayers.

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Resistive switching characteristics in memristors with Al₂O₃/TiO₂ and TiO₂/Al₂O₃ bilayers

Cited by 29 publications

References 38 publications

Influence of Oxidant Gas of Atomic Layer Deposition on Electrical Characteristics of Al<sub>2</sub>O<sub>3</sub> films

Influence of Oxidant Gas of Atomic Layer Deposition on Electrical Characteristics of Al<sub>2</sub>O<sub>3</sub> films

Multibit memory operation of metal-oxide bi-layer memristors

Contact Engineering Approach to Improve the Linearity of Multilevel Memristive Devices

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