Bipolar Electrochemical Mechanism for Mass Transfer in Nanoionic Resistive Memories

Tian, Xuezeng; Yang, Shize; Zeng, Min; Wang, Lifen F.; Wei, Jiake; Li, Zhiheng; Wang, Wenlong; Bai, Xuedong

doi:10.1002/adma.201400127

Cited by 99 publications

(85 citation statements)

References 31 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: 73%

“…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).…”

mentioning

confidence: 99%

“…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] .…”

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confidence: 99%

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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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“…Being a poor Ag ion conductor and unable to dissolve Ag chemically, HfOx makes Ag + easy to be chemically reduced within the dielectrics due to low ion mobility and low redox reaction rate, yielding the observed cone shaped Ag filament which grows from the Ag source rather than having Ag deposition on the opposite anode. [47,48] However, neither of the protrusions completely bridged the dielectric between the top and bottom electrodes, which is different from the behavior typically observed in CBRAM [46,48,49] . The incomplete bridging was further verified by EDS line scans of the Ag peak along the white dashed lines shown in Figure 4(e), which also showed a clear narrowing of the dielectric layer thickness.…”

Section: Resultscontrasting

confidence: 43%

Anatomy of Ag/Hafnia‐Based Selectors with 10¹⁰ Nonlinearity

et al. 2017

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A novel Ag/oxide‐based threshold switching device with attractive features including ≈1010 nonlinearity is developed. High‐resolution transmission electron microscopic analysis of the nanoscale crosspoint device suggests that elongation of an Ag nanoparticle under voltage bias followed by spontaneous reformation of a more spherical shape after power off is responsible for the observed threshold switching.

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“…37 The inferred growth direction of Cu filament in Cu/ZnS/Pt is similar to that in oxide-based ECM cells. 17,[37][38][39][40][41] The formation of the Cu filament may result from the bipolar electrochemical mass transfer of Cu nanoclusters in ZnS. 17,41 As mentioned previously, the As 2 S 3 :Ag-, 33 GeSe:Ag-, 34 GeS:Cu-, 35 and Ag 2 S-based (Ref.…”

Section: Resultsmentioning

confidence: 99%

Mechanism for resistive switching in chalcogenide-based electrochemical metallization memory cells

Zhuge

et al. 2015

AIP Advances

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It has been reported that in chalcogenide-based electrochemical metallization (ECM) memory cells (e.g., As2S3:Ag, GeS:Cu, and Ag2S), the metal filament grows from the cathode (e.g., Pt and W) towards the anode (e.g., Cu and Ag), whereas filament growth along the opposite direction has been observed in oxide-based ECM cells (e.g., ZnO, ZrO2, and SiO2). The growth direction difference has been ascribed to a high ion diffusion coefficient in chalcogenides in comparison with oxides. In this paper, upon analysis of OFF state I–V characteristics of ZnS-based ECM cells, we find that the metal filament grows from the anode towards the cathode and the filament rupture and rejuvenation occur at the cathodic interface, similar to the case of oxide-based ECM cells. It is inferred that in ECM cells based on the chalcogenides such as As2S3:Ag, GeS:Cu, and Ag2S, the filament growth from the cathode towards the anode is due to the existence of an abundance of ready-made mobile metal ions in the chalcogenides rather than to the high ion diffusion coefficient.

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Bipolar Electrochemical Mechanism for Mass Transfer in Nanoionic Resistive Memories

Cited by 99 publications

References 31 publications

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

Anatomy of Ag/Hafnia‐Based Selectors with 10¹⁰ Nonlinearity

Mechanism for resistive switching in chalcogenide-based electrochemical metallization memory cells

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Bipolar Electrochemical Mechanism for Mass Transfer in Nanoionic Resistive Memories

Cited by 99 publications

References 31 publications

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

Anatomy of Ag/Hafnia‐Based Selectors with 1010 Nonlinearity

Mechanism for resistive switching in chalcogenide-based electrochemical metallization memory cells

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Anatomy of Ag/Hafnia‐Based Selectors with 10¹⁰ Nonlinearity