Engineering synaptic plasticity through the control of oxygen vacancy concentration for the improvement of learning accuracy in a Ta2O5 memristor

Hwang, Hyun-Gyu; Pyo, Yeon; Woo, Jong‐Un; Kim, In-Su; Kim, Sun-Woo; Kim, Dae-Su; Kim, Bumjoo; Jeong, Jichai; Nahm, Sahn

doi:10.1016/j.jallcom.2022.163764

Cited by 20 publications

(12 citation statements)

References 47 publications

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“…On the other hand, in case of WO 3−x layers (S75 and S77) with large V O s density, continuous increase (decrease) of current on application of negative (positive) DC bias with magnitude lower than V set (V reset ) on the top W-electrode indicates gradual strengthening (weakening) of the CFs. Similar observation had been reported for various substoichiometric metal oxide memristors possessing large V O s concentration [20,53,54]. A schematic of V O s and CF growth under P-pulses in the V O rich WO 3−x memristors is presented in figure 9.…”

Section: Switching Mechanismsupporting

confidence: 82%

“…Tunable digital to analogue RS by V O engineering and manifestation of synaptic features in Nb 2 O 5 thin films have been demonstrated by Xu et al [19]. Hwang et al reported significant improvement of conduction modulation linearity and pattern recognition efficiency upon increasing V O s concentration in Ta 2 O 5 thin films [20]. In case of TiO x -based memristors increase of V O s by means of ion beam irradiation, as well as incorporation of a V O -rich TiO y layer have been found to improve their neuromorphic characteristics [21,22].…”

Section: Introductionmentioning

confidence: 95%

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Tuning resistive switching properties of WO₃₋_x-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

Rudrapal

Biswas²,

Jana³

et al. 2023

J. Phys. D: Appl. Phys.

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High density memory storage capacity, in-memory computation and meuromorphic computing utilizing memristors are expected to solve the limitation of von-Neumann computing architecture. Controlling oxygen vacancy (VO) defects in metal oxide thin film based memristors holds the potential of designing resistive switching (RS) properties for memroy storage and neuromorphic applications. Herein, we report on RS characteristics of CMOS compatible WO3-x based memristors modulated by precisely controlled oxygen non-stoichiometry. Switchability of the resistance states has been found to depend strongly on the VOs concentration in the WO3-x layer. Depending on x, the memristors exhibited forming-free bipolar, forming-required bipolar, and non-formable characteristics. Devices with moderate VOs concentration (~5.8×1020 cm-3) exhibited a large Roff/Ron ratio of ~6500, and reset voltage-controlled multi-level resistance states. A forming-free, stable multi-level RS has been realized for a memristor possessing VOs concentration of ~6.2×1020 cm-3. WO3-x-based memristors with higher VOs concentrations (~8.9×1020 cm-3-1×1021 cm-3) exhibited lower initial resistance, low Roff/Ron ratios (~15-63) and forming-free synaptic functions with reasonable conduction modulation linearity. Investigation of the conduction mechanism suggests that tailoring VOs concentration modifies the formation and dimension of the conducting filaments and the Schottky barrier height at the WO3-x/Pt interface, which paves the way for designing WO3-x -based memristors for memory storage and neuromorphic applications.

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Section: Switching Mechanismsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 95%

Tuning resistive switching properties of WO₃₋_x-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

Rudrapal

Biswas²,

Jana³

et al. 2023

J. Phys. D: Appl. Phys.

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“…By applying a positive bias at the Ag TE, the negatively charged oxygen ions migrate toward the TE and are eventually adsorbed by the TE or reduced to O 2 , whereas oxygen vacancies are created around the interface of Ag/TiO 2. ,, The positively charged oxygen vacancies are driven to the BE and assemble a conducting channel through defects, such as grain boundaries and cracks. When the bias voltage reaches V set , CFs (consisting of oxygen vacancies) form between the TE and BE and the resistance immediately changes from the HRS to LRS.…”

Section: Resultsmentioning

confidence: 99%

Optimization of the Cycle Numbers of TiO₂ Resistive Random-Access Memory Devices by Annealing

Yao

Zhao

et al. 2023

ACS Appl. Electron. Mater.

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Resistance switching (RS) devices that are based on titanium dioxide (TiO2) nanomaterials have recently attracted substantial research interest because of their simple preparation technology and potential applications in the applications of memory devices. In this paper, the RS characteristics of TiO2-based memristors were regulated by changing the crystal structure of the TiO2 film. Resistive switching memory, consisting of Ag/amorphous TiO2/Ti fabricated by anodic oxidation, exhibited poor cycling stability. Annealing was applied to the anodized sample over the temperature range of 230–680 °C, and the structure of TiO2 was investigated throughout the process. Amorphous TiO2 transformed into the anatase phase as the annealing temperature was increased to 280 °C and the stable cycle number of the device peaked at 51. By annealing at >450 °C, TiO2 was gradually transformed into the rutile phase, and the stable cycle number of the device decreased to 7. X-ray photoelectron spectroscopy confirmed that the concentration of oxygen vacancies in rutile TiO2 decreased with increasing temperature compared with that in anatase TiO2, resulting in the declining performance of the device. This work presents a low-cost annealing process to prepare stable anatase TiO2-based memristors, which will promote the industrialization of the devices for nonvolatile memory applications in the future.

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“…[4,39] RS is performed by applying voltages of opposite polarities, or, in other words, in the bipolar operation mode. The most common oxide materials (frequently transition metal oxides) used in these devices are HfO 2 , [40,41] Ta 2 O 5 , [42][43][44] TiO 2 , [45] ZrO 2 , [46,47] Al 2 O 3 , [48] and nanolaminates of them. [45,49,50] Among the different alternatives, HfO 2 -based resistive memories have achieved one of the best performances in terms of reproducibility with welldefined resistance states and good device endurance.…”

Section: Introductionmentioning

confidence: 99%

Variability in Resistive Memories

Roldán

Miranda

Maldonado

et al. 2023

Advanced Intelligent Systems

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Research and development efforts in the nonvolatile memory arena are focused on a reduced set of innovative components, among which we can include memristors. [1,2] Memristors are expected to be key players in the electronics landscape of the coming years largely because of the powerful applications that stand upon their unique features. [1,[3][4][5] The switching mechanisms behind memristors differ significantly depending on the physical properties of the structures and the materials involved. [1,[3][4][5][6][7] To list some of these mechanisms, we can highlight those devices based on phase-change materials, which can be switched reversibly between amorphous and crystalline phases with different electrical resistivity (phasechange memories, PCMs); [8] devices that take advantage of the magnetic and electrical properties exhibited by some materials with different architectures (magnetic RAMs, MRAMs); [9] also structures where materials with switchable electrical polarization give rise to hysteresis curves of the polarization versus electrical field that can be engineered for storing information (ferroelectric FET, FFET); [10] and, finally, resistive RAMs (RRAMs) where the dielectric conduction properties are altered by means of the internal ion movement and concurrent redox reactions used to generate different resistive states. [1,3,11,12]

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Engineering synaptic plasticity through the control of oxygen vacancy concentration for the improvement of learning accuracy in a Ta2O5 memristor

Cited by 20 publications

References 47 publications

Tuning resistive switching properties of WO₃₋_x-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

Tuning resistive switching properties of WO₃₋_x-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

Optimization of the Cycle Numbers of TiO₂ Resistive Random-Access Memory Devices by Annealing

Variability in Resistive Memories

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Engineering synaptic plasticity through the control of oxygen vacancy concentration for the improvement of learning accuracy in a Ta2O5 memristor

Cited by 20 publications

References 47 publications

Tuning resistive switching properties of WO3−x-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

Tuning resistive switching properties of WO3−x-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

Optimization of the Cycle Numbers of TiO2 Resistive Random-Access Memory Devices by Annealing

Variability in Resistive Memories

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Tuning resistive switching properties of WO₃₋_x-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

Tuning resistive switching properties of WO₃₋_x-memristors by oxygen vacancy engineering for neuromorphic and memory storage applications

Optimization of the Cycle Numbers of TiO₂ Resistive Random-Access Memory Devices by Annealing