Real‐Time Observation on Dynamic Growth/Dissolution of Conductive Filaments in Oxide‐Electrolyte‐Based ReRAM

Liu, Qi; Sun, Jun; Lv, Hangbing; Long, Shibing; Yin, Kuibo; Wan, Neng; Li, Yingtao; Sun, Litao; Liu, Ming

doi:10.1002/adma.201104104

Cited by 558 publications

(521 citation statements)

References 34 publications

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“…Up to this point, the behaviour of Ag nanoparticles in SiO x N y is similar to previous observations, which have been interpreted as electrochemical reactions at effectively bipolar electrodes [21][22][23][24][25][26] . We next turned off the power at 5.0s to observe the spontaneous relaxation, which is critical for understanding the dynamics of these devices, but has not been previously reported to the best of our knowledge.…”

supporting

confidence: 88%

“…This model links electrical, nano-mechanical and thermal degrees of freedom (Methods). The model results here did not include redox reactions, although they can be added in order to more closely resemble the electrochemical models proposed previously [21][22][23][24][25][26] .…”

mentioning

confidence: 99%

“…S1-S2). These devices are similar to electrochemical metallization memory (ECM) [21][22][23][24][25][26] cells in terms of utilizing mobile species of noble metals, but they differ substantially in terms of the structural symmetry and operating voltage polarities, metal concentration and profile, and transient switching behaviour. An applied voltage above an apparent threshold abruptly switched the device to a conductance state limited by an external compliance current (Fig. 1b).…”

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Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

et al. 2016

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The accumulation and extrusion of Ca 2+ in the pre-and postsynaptic compartments play a critical role in initiating plastic changes in biological synapses. To emulate this fundamental process in electronic devices, we developed diffusive Ag-in-oxide memristors with a temporal response during and after stimulation similar to that of the synaptic Ca 2+ dynamics. In situ high-resolution transmission electron microscopy and nanoparticle dynamics simulations both demonstrate that Ag atoms disperse under electrical bias and regroup spontaneously under zero bias because of interfacial energy 2 minimization, closely resembling synaptic influx and extrusion of Ca 2+ , respectively.The diffusive memristor and its dynamics enable a direct emulation of both short-and long-term plasticity of biological synapses and represent a major advancement in hardware implementation of neuromorphic functionalities.CMOS circuits have been employed to mimic synaptic Ca 2+ dynamics, but three-terminal devices bear limited resemblance to bio-counterparts at the mechanism level and require significant numbers and complex circuits to simulate synaptic behavior [1][2][3] . A substantial reduction in footprint, complexity and energy consumption can be achieved by building a two-terminal circuit element, such as a memristor directly incorporating Ca 2+ -like dynamics.Various types of memristors based on ionic drift (drift-type memristor) 4-8 have recently been utilized for this purpose in neuromorphic architectures [9][10][11][12][13][14][15] . Although qualitative synaptic functionality has been demonstrated, the fast switching and non-volatility of drift memristors optimized for memory applications do not faithfully replicate the nature of plasticity. Similar issues also exist in MOS-based memristor emulators [16][17][18] , although they are capable of simulating a variety of synaptic functions including spike-timing-dependent plasticity (STDP). Recently, Lu's group adopted second-order drift memristors to approximate the Ca 2+ dynamics of chemical synapses by utilizing thermal dissipation 19 or mobility decay 20 , which successfully demonstrated STDP with non-overlapping spikes and other synaptic functions, representing a significant step towards bio-realistic synaptic devices. This approach features repeatability and simplicity, but the significant differences of the dynamical response from actual synapses limit the fidelity and variety of desired synaptic functions. A device with similar physical behavior as the biological Ca 2+ dynamics would enable improved emulation of synaptic function and broad applications to neuromorphic computing. Here we report such an emulator, which is a memristor based on metal atom 3 diffusion and spontaneous nanoparticle formation, as determined by in situ high-resolution transmission electron microscopy (HRTEM) and nanoparticle dynamics simulations. The dynamical properties of the diffusive memristors were confirmed to be functionally equivalent to Ca 2+ in bio-synapses, and their operating characteri...

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Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

et al. 2016

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“…1-3 Among various RRAMs, electrochemical metallization (ECM) cells based on the formation and dissolution of nanoscaled metal filaments have attracted considerable attention due to their simple structure, high switching speed, low power consumption, and outstanding scalability. [4][5][6] Generally, the ECM cell comprises a dielectric layer sandwiched between an electrochemically active electrode (usually, Ag or Cu) and an inert electrode (e.g., Pt or W). When a positive voltage is applied to the active electrode, conductive filament is formed due to the field-assisted injection and transport of metal cations thereby defining a low resistance state (LRS).…”

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Bidirectional threshold switching characteristics in Ag/ZrO2/Pt electrochemical metallization cells

Wang

et al. 2016

AIP Advances

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A bidirectional threshold switching (TS) characteristic was demonstrated in Ag/ZrO2/Pt electrochemical metallization cells by using the electrochemical active Ag electrode and appropriate programming operation strategies The volatile TS was stable and reproducible and the rectify ratio could be tuned to ∼107 by engineering the compliance current. We infer that the volatile behavior is essentially due to the moisture absorption in the electron beam evaporated films, which remarkably improved the anodic oxidation as well as the migration of Ag+ ions. The resultant electromotive force would act as a driving force for the metal filaments dissolution, leading to the spontaneous volatile characteristics. Moreover, conductance quantization behaviors were also achieved owing to formation and annihilation of atomic scale metal filaments in the film matrix. Our results illustrate that the Ag/ZrO2/Pt device with superior TS performances is a promising candidate for selector applications in passive crossbar arrays.

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“…The second one was solid electrolytes with Cu or Ag electrode. [33][34][35][36][37] During the set and reset operation, the formation of metallic filament composed of Cu or Ag connecting electrodes and its rupture were experimentally proved. In these two kinds of materials, the forming process is not required in general cases.…”

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confidence: 99%

In-situ transmission electron microscopy of conductive filaments in NiO resistance random access memory and its analysis

Fujii

Arita

Hamada

et al. 2013

Journal of Applied Physics

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We used thermal oxidization at various temperatures to prepare NiO/Pr-Ir for use in resistance random access memory (ReRAM) samples. In-situ transmission electron microscopy (TEM) was used to investigate the forming process of these ReRAM samples, where a needle-shaped top electrode of Pt-Ir was attached to the NiO/Pt-Ir ReRAM layer. The forming voltage initializing the NiO layer increased at an oxidization temperature of between 200 and 400 C. In this process, conductive bridges, which are thought to be conductive filaments of a ReRAM, appeared, and their sizes showed a correlation with the injection power. It was as small as about 300 nm 2 when the injection power was 10 À6 W. Energy dispersive X-ray spectroscopy was used to analyze the bridge, and it was experimentally confirmed that the oxygen content of the bridge was lower than that of the initial NiO layer. However, these bridges in the low resistance state did not show further ReRAM switching to the high resistance state inside of a TEM instrument. To check the reason of this result, we investigated samples outside of the TEM instrument, which had similar geometry to that of TEM specimens. They showed the ReRAM switching in air ambient but not in vacuum. Combining these results inside and outside of the TEM instrument, it can be concluded that the existence of oxygen around the conductive filament plays an important role. This supports the filament redox model on the ReRAM operation. V C 2013 American Institute of Physics.

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Real‐Time Observation on Dynamic Growth/Dissolution of Conductive Filaments in Oxide‐Electrolyte‐Based ReRAM

Cited by 558 publications

References 34 publications

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

Bidirectional threshold switching characteristics in Ag/ZrO2/Pt electrochemical metallization cells

In-situ transmission electron microscopy of conductive filaments in NiO resistance random access memory and its analysis

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