Volatile and nonvolatile selective switching of a photo-assisted initialized atomic switch

Hino, Takami; Hasegawa, Tsuyoshi; Tanaka, Hirofumi; Tsuruoka, Tohru; Terabe, Kazuya; Ogawa, Takuji; Aono, Masakazu

doi:10.1088/0957-4484/24/38/384006

Cited by 25 publications

(22 citation statements)

References 32 publications

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“…The mechanism of operation of these devices is known as the formation and rupture of a conductive bridge path (e.g., metallic filament) in solid-electrolyte layers. [36][37][38][39] Because extrinsic Ag ions have a large diffusion coefficient (i.e., are fast diffusers), Ag ions can easily migrate in the ZnO matrix along the applied electric field. 40,41 After they reached the bottom electrode through the ZnO layer without agglomerating, they formed filaments by combining with electrons at the bottom electrode interface (Figure 2c).…”

Section: Resultsmentioning

confidence: 99%

“…In addition, the electric-field has an important effect on filament instability. 38,43,44 In this work, a weak electric field was applied to the electrode. It could not reach the top electrode because low voltage was applied to the 40-nm-thick oxide layer.…”

Section: Resultsmentioning

confidence: 99%

“…Experimental verification to show the formation of conductive filaments has been reported. 37,38 To understand the Ag filament formation in the ZnO layer, first-principle DFT calculations were performed. Because Ag ions are preferentially located in Zn sites, we focused on the energetics of the substitutional Ag 0…”

Section: Resultsmentioning

confidence: 99%

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Reliable current changes with selectivity ratio above 109 observed in lightly doped zinc oxide films

Han

Lee

2017

NPG Asia Mater

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Low-power operation of semiconductor devices is crucial for energy conservation. In particular, energy-efficient devices are essential in portable electronic devices to allow for extended use with a limited power supply. However, unnecessary currents always exist in semiconductor devices, even when the device is in its off state. To solve this problem, it is necessary to use switch devices that can turn active devices on and off effectively. For this purpose, high on/off current selectivity with ultra-low off-current and high on-current is required. Here, we report a novel switch behavior with over 10 9 selectivity, a high on-current density of 1 MA cm -2 , an ultra-low off-current density of 1 mA cm -2 , excellent thermal stability up to 250°C and abrupt turn-on with 5 mV per decade in solution-processed silver-doped zinc oxide thin films. The selection behavior is attributed to light doping of silver ions in zinc oxide films during electrochemical deposition to generate atomic-scale narrow conduction paths, which can be formed and ruptured at low voltages. Device simulation showed that the new selector devices may be used in ultra-highdensity memory devices to provide excellent operation margins and extremely low power consumption.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Reliable current changes with selectivity ratio above 109 observed in lightly doped zinc oxide films

Han

Lee

2017

NPG Asia Mater

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“…The Cu cations are reduced at the Pt electrode/TiO 2 electrolyte interface, where Cu clusters are formed through nucleation followed by a growth process (Figure 5a,b). Hino et al presented a light irradiation assisted atomic switch, [46] and Liu et al suggested the presence of δ-Cu phase incurred volatile switching. There are several previous studies dealing with threshold switching behavior of ECM-based ReRAM.…”

Section: Resultsmentioning

confidence: 99%

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device

Kim

Yoon

Park

et al. 2017

Adv Elect Materials

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and rupture of the metallic conducting filament (CF) composed of active metal atoms, typically Ag and Cu, are responsible for the resistance switching. Unlike other resistive switching devices, the active metal constitutes one of the electrodes which is critically involved in the redox reaction of CF formation and rupture in ECM devices. According to the conventional ECM theory, the cations generated from the anode (active metal) migrate through the solid electrolyte layer when a positive bias is applied to the active metal electrode. The migrated metal cations receive electrons at the cathode (inert metal)/electrolyte interface, and are reduced to metal atoms forming the growing CF. After a series of reduction processes, metallic CF(s) is (are) formed, and current flows through them, thus, the device resistance state becomes a low resistance state (LRS), which corresponds to set switching. When the bias polarity is reversed, a reverse reaction occurs, and the device turns back to a high resistance state (HRS), which is most probably mediated by the oxidation of the metal atoms at the filament tip near the active metal electrode. This corresponds to reset switching. In this conventional ECM model based on the redox reaction of active metal atoms, the idea that a conical-shaped filament grows from the cathode/ electrolyte interface toward the active electrode (anode) and that ECM devices show bipolar resistive switching (BRS) has been widely accepted. [6,7] However, counterarguments against the conventional ECM filament forming theory, covering not only the reset polarity but also the filament geometry, have been discovered in recent years. [8,9] These studies revealed that the filament growth can be extensively influenced by the detailed material parameters, such as the type of electrolyte materials as well as the cation/electron mobility and its redox rate. [9][10][11][12][13] With the aid of in situ transmission electron microscopy (TEM) and conductive atomic force microscopy techniques, real-time image of growth and rupture of conducting filament have been reported. [14,15] These factors contribute not only to the initiation location of the filament growth but also to the consequent shape of the grown filament. In addition, studies objecting to the incumbent ECM reset mechanism theory have been reported recently. According to the conventional ECM theory, due to its redox reaction based characteristics, only bipolarThe electrochemical metallization (ECM) cell is a feasible contender for high density resistance switching random access memory or neuromorphic devices. This work elucidates the detailed switching model based on the Cu conducting filament (CF) configuration and the interplay between the Joule heating and electric field effects in the Pt/TiO 2 /Cu ECM cell, which can explain the switching behaviors both in accordance and discordance with the conventional ECM theory. The Cu CF configuration is varied from the conventional conical one for a small compliance current (I cc , ≈1 mA) to the hourglass or eve...

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“…18 This limitation is for instance utilized in volatile and nonvolatile selective switching of photo-assisted atomic switches. 19,20 Decision making based on these atomic switches was very recently proposed theoretically by Kim et al 21 In this study, we extend the function of atomic switches so that they can achieve the 'tug of war' operation. In conventional gap-type atomic switches, growth and shrinkage of a metal filament between two electrodes, a solid electrolyte electrode such as α-Ag 2+δ S and a counter metal electrode, are controlled, see Fig.…”

Section: Introductionmentioning

confidence: 95%

Ag₂S atomic switch-based ‘tug of war’ for decision making

Lutz

Hasegawa

Chikyow³

2016

Nanoscale

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For a computing process such as making a decision, a software controlled chip of several transistors is necessary. Inspired by how a single cell amoeba decides its movements, the theoretical 'tug of war' computing model was proposed but not yet implemented in an analogue device suitable for integrated circuits. Based on this model, we now developed a new electronic element for decision making processes, which will have no need for prior programming. The devices are based on the growth and shrinkage of Ag filaments in α-Ag2+δS gap-type atomic switches. Here we present the adapted device design and the new materials. We demonstrate the basic 'tug of war' operation by IV-measurements and Scanning Electron Microscopy (SEM) observation. These devices could be the base for a CMOS-free new computer architecture.

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Volatile and nonvolatile selective switching of a photo-assisted initialized atomic switch

Cited by 25 publications

References 32 publications

Reliable current changes with selectivity ratio above 109 observed in lightly doped zinc oxide films

Reliable current changes with selectivity ratio above 109 observed in lightly doped zinc oxide films

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device

Ag₂S atomic switch-based ‘tug of war’ for decision making

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Volatile and nonvolatile selective switching of a photo-assisted initialized atomic switch

Cited by 25 publications

References 32 publications

Reliable current changes with selectivity ratio above 109 observed in lightly doped zinc oxide films

Reliable current changes with selectivity ratio above 109 observed in lightly doped zinc oxide films

Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO2/Cu Electrochemical Metallization Device

Ag2S atomic switch-based ‘tug of war’ for decision making

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Filament Shape Dependent Reset Behavior Governed by the Interplay between the Electric Field and Thermal Effects in the Pt/TiO₂/Cu Electrochemical Metallization Device

Ag₂S atomic switch-based ‘tug of war’ for decision making