Metallic filamentary conduction in valence change-based resistive switching devices: the case of TaO<sub>x</sub> thin film with <i>x</i> ∼ 1

Rosário, Carlos M. M.; Thöner, Bo; Schönhals, Alexander; Menzel, Stephan; Meledin, Alexander; Barradas, N.P.; Alves, E.; Wuttig, Matthias; Waser, Rainer; Соболев, Н. А.; Wouters, Dirk J.

doi:10.1039/c9nr05285b

Cited by 21 publications

(19 citation statements)

References 75 publications

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“…The devices are programmed by applying electrical stimuli, during which an n-conducting filament consisting of mobile donors is either formed (SET) or ruptured (RESET). Spectroscopic studies have identified these mobile donors as oxygen vacancies. − Especially for TaO x -based devices also a movement of metallic cations was observed. − During the SET, a negative voltage is applied to the active electrode (attracting mobile donors) and a positive voltage during the RESET (repelling mobile donors). As the voltages required for the SET and RESET have opposite signs, this corresponds to a bipolar switching mode.…”

Section: Introductionmentioning

confidence: 99%

Intrinsic RESET Speed Limit of Valence Change Memories

Witzleben

Wiefels

Kindsmüller

et al. 2021

ACS Appl. Electron. Mater.

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During the past decade, valence change memory (VCM) has been extensively studied due to its promising features, such as a high endurance and fast switching times. The information is stored in a high resistive state (HRS) and a low resistive state (LRS). It can also be operated in two different writing schemes, namely a unipolar switching mode (LRS and HRS are written at the same voltage polarity) and a bipolar switching mode (LRS and HRS are written at opposite voltage polarities). VCM, however, still suffers from a large variability during writing operations and also faults occur, which are not yet fully understood and, therefore, require a better understanding of the underlying fault mechanisms. In this study, a new intrinsic failure mechanism is identified, which prohibits RESET times (transition from LRS to HRS) faster than 400 ps and possibly also limits the endurance. We demonstrate this RESET speed limitation by measuring the RESET kinetics of two valence change memory devices (namely Pt/TaO x /Ta and Pt/ZrO x /Ta) in the time regime from 50 ns to 50 ps, corresponding to the fastest writing time reported for VCM. Faster RESET times were achieved by increasing the applied pulse voltage. Above a voltage threshold it was, however, no longer possible to reset both devices. Instead a unipolar SET (transition from HRS to LRS) event occurred, preventing faster RESET times. The occurrence of the unipolar SET is attributed to an oxygen exchange at the interface to the Pt electrode, which can be suppressed by introducing an oxygen blocking layer at this interface, which also allowed for 50 ps fast RESET times.

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Section: Introductionmentioning

confidence: 99%

Intrinsic RESET Speed Limit of Valence Change Memories

Witzleben

Wiefels

Kindsmüller

et al. 2021

ACS Appl. Electron. Mater.

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“…This also appears to be unlikely. Recent conductivity measurements of substoichiometric TaO x films indicate that the compositions that can produce significant current densities and Joule heating in the filament at typical applied voltage values are close to 1:1, i.e., composition of TaO. , …”

Section: Discussionmentioning

confidence: 99%

Exchange of Ions across the TiN/TaO_x Interface during Electroformation of TaO_x-Based Resistive Switching Devices

Cullen

Goodwill

et al. 2020

ACS Appl. Mater. Interfaces

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The valence change model describes the resistive switching in metal oxide-based devices as due to electroreduction of the oxide and subsequent electromigration of oxygen vacancies. Here, we present cross-sectional X-ray energy-dispersive spectroscopy elemental maps of Ta, O, N, and Ti in electroformed TiN/TaO2.0/TiN structures. O, N, and Ti were exchanged between the anode and the functional oxide in devices formed at high power (∼1 mW), but the exchange was below the detection limit at low power (<0.5 mW). All structures exhibit a similar Ta-enriched and O-depleted filament formed by the elemental segregation in the functional oxide by the temperature gradient. The elemental interchange is interpreted as due to Fick’s diffusion caused by high temperatures in the gap of the filament and is not an essential part of electroformation.

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“…Unlike traditional silicon‐based memory devices with binary memory states, organic resistive memory devices possess multiple resistive states which enhance their data storage capacity [16] . There are many switching (between the conduction states) mechanism proposed and established in organic devices, mainly categorized into thermochemical reaction, ion migration, interfacial reaction, charge trapping/de‐trapping, charge transfer, electrochemical redox reaction, and conformational change [17–21] . If the states can retain the assigned binary states for longer duration and in the absence of an applied potential, it is called a non‐volatile resistive memory device [22,23] .…”

Section: Introductionmentioning

confidence: 99%

Irreversible Resistive State Switching in Devices with a Homoleptic Cobalt(II) Complex Active Layer

Barman

Khatua

Goswami

et al. 2021

Chemistry An Asian Journal

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Molecules with bi‐stable electronic transport behaviour have been in upfront research topics of the molecular semiconductor devices in the past few decades due to the use of such materials in resistive data storage devices. Transition metal complexes (TMC) are expected to be potential candidates in regard to the tunable and manifold redox behaviour expecting multiple bulk transport states. Finding alternate mechanisms in such devices with TMC as the active layer materials would revoke the multifaceted approach to the functional gain. We have succeeded in demonstrating write once‐read many (WORM) type of resistive memory device using a homoleptic Cobalt(II) (Co(II)) complex with large on/off current ratio ensuring the easy readout process at lower voltage. The advantage of this device was the turn on voltage was found to be the low (<2.7 V) operational voltage and the success ratio of the devices were more than 83%. The durability of the stored data was found to be more than 35,000 seconds which ensures the stability of the bistable state in the fabricated devices. Such ambient stable, solution processable devices are important for the large‐scale printable devices. The manuscript describes the preparation, optical and electrochemical characterisation of the metal complex used along with a detailed mechanistic investigations and electrical characterisation of memory device obtained from a stable cobalt complex.

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Metallic filamentary conduction in valence change-based resistive switching devices: the case of TaO_x thin film with x ∼ 1

Abstract: A detailed study of the electrical transport in TaOx thin films with x ∼ 1 provides an insight into the conduction in conductive filaments inside Ta2O5-based resistive switching devices.

Cited by 21 publications

References 75 publications

Intrinsic RESET Speed Limit of Valence Change Memories

Intrinsic RESET Speed Limit of Valence Change Memories

Exchange of Ions across the TiN/TaO_x Interface during Electroformation of TaO_x-Based Resistive Switching Devices

Irreversible Resistive State Switching in Devices with a Homoleptic Cobalt(II) Complex Active Layer

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Metallic filamentary conduction in valence change-based resistive switching devices: the case of TaOx thin film with x ∼ 1

Abstract: A detailed study of the electrical transport in TaOx thin films with x ∼ 1 provides an insight into the conduction in conductive filaments inside Ta2O5-based resistive switching devices.

Cited by 21 publications

References 75 publications

Intrinsic RESET Speed Limit of Valence Change Memories

Intrinsic RESET Speed Limit of Valence Change Memories

Exchange of Ions across the TiN/TaOx Interface during Electroformation of TaOx-Based Resistive Switching Devices

Irreversible Resistive State Switching in Devices with a Homoleptic Cobalt(II) Complex Active Layer

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Product

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Metallic filamentary conduction in valence change-based resistive switching devices: the case of TaO_x thin film with x ∼ 1

Exchange of Ions across the TiN/TaO_x Interface during Electroformation of TaO_x-Based Resistive Switching Devices