The Experts below are selected from a list of 4008 Experts worldwide ranked by ideXlab platform
Yoshio Nishi - One of the best experts on this subject based on the ideXlab platform.
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hfo 2 ti interface mediated Conductive Filament formation in rram an ab initio study
IEEE Transactions on Electron Devices, 2018Co-Authors: Boubacar Traore, Blanka Magyarikope, Philippe Blaise, Benoit Sklenard, Elisa Vianello, Yoshio NishiAbstract:We address the role of the Ti/HfO2 interface on the Conductive Filament (CF) formation within the context of oxide-based resistive random access memories (OxRRAMs). We investigate oxygen defects formation and diffusion at the interface through ab initio calculations. The calculated diffusion energy barriers compare well with the available experimental data. Through the interface region charge analysis and the associated energies with O defect formation and migration into Ti, our results support a probable CF growth from the interface region toward the electron injecting electrode, which acts as a cathode. Hence, for a Ti/HfO2-based OxRRAM supported by the calculation results, we present a pertinent CF growth model by considering its earliest stages, which is relevant for device modeling.
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HfO2/Ti Interface Mediated Conductive Filament Formation in RRAM: An Ab Initio Study
IEEE Transactions on Electron Devices, 2018Co-Authors: Boubacar Traore, Blanka Magyari-köpe, Philippe Blaise, Benoit Sklenard, Elisa Vianello, Yoshio NishiAbstract:We address the role of the Ti/HfO2 interface on the Conductive Filament (CF) formation within the context of oxide-based resistive random access memories (OxRRAMs). We investigate oxygen defects formation and diffusion at the interface through ab initio calculations. The calculated diffusion energy barriers compare well with the available experimental data. Through the interface region charge analysis and the associated energies with O defect formation and migration into Ti, our results support a probable CF growth from the interface region toward the electron injecting electrode, which acts as a cathode. Hence, for a Ti/HfO2-based OxRRAM supported by the calculation results, we present a pertinent CF growth model by considering its earliest stages, which is relevant for device modeling.
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HfO 2 /Ti Interface Mediated Conductive Filament Formation in RRAM: An Ab Initio Study
IEEE Transactions on Electron Devices, 2018Co-Authors: Boubacar Traore, Blanka Magyari-köpe, Philippe Blaise, Benoit Sklenard, Elisa Vianello, Yoshio NishiAbstract:We address the role of the Ti/HfO2 interface on the Conductive Filament (CF) formation within the context of oxide-based resistive random access memories (OxRRAMs). We investigate oxygen defects formation and diffusion at the interface through ab initio calculations. The calculated diffusion energy barriers compare well with the available experimental data. Through the interface region charge analysis and the associated energies with O defect formation and migration into Ti, our results support a probable CF growth from the interface region toward the electron injecting electrode, which acts as a cathode. Hence, for a Ti/HfO2-based OxRRAM supported by the calculation results, we present a pertinent CF growth model by considering its earliest stages, which is relevant for device modeling.
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H-treatment impact on Conductive-Filament formation and stability in Ta2O5-based resistive-switching memory cells
Journal of Applied Physics, 2015Co-Authors: Ludovic Goux, Blanka Magyari-köpe, Yoshio Nishi, Ja-yong Kim, Augusto Redolfi, Malgorzata JurczakAbstract:In this article, we evidence the lower formation energy and improved stability of the Conductive Filament (CF) formed in TiN\Ta2O5\Ta resistive-switching memory cells treated in NH3 atmosphere at 400 °C. This annealing treatment results in (i) lower forming voltage, (ii) lower CF resistance, and (iii) longer retention lifetime of the oxygen-vacancy (Vo) chain constituting the CF. Atomistic insights into these processes are provided by ab initio calculations performed for hydrogen (H) species incorporated in non-stoichiometric Ta2O5 supercells: (i) Vo formation energy is reduced by the presence of H, (ii) Vo-chain CF conductivity is increased by Vo + OH complex formation, and (iii) Vo-chain retention is strengthened by the stable Vo + OH complex. As a result, efficient CF formation and excellent state stability are obtained after 15 days at 250 °C.
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First-principles investigation of the Conductive Filament configuration in rutile TiO 2-x ReRAM
MRS Proceedings, 2012Co-Authors: Liang Zhao, Seong-geon Park, Blanka Magyari-köpe, Yoshio NishiAbstract:ABSTRACTThe interactions and ordering of oxygen vacancies in rutile TiO2 were thoroughly investigated by density functional calculations to search for atomic configurations of the Conductive Filament. As random isolated vacancies could not support the low-resistance state conduction in TiO2 ReRAM, vacancy ordering was introduced in [110] and [001] directions of the lattice to study the electronic structures. The calculation results revealed that a di-vacancy chain in [001] direction makes the electrons delocalized in that direction, which is identified as a possible configuration of the Conductive Filament. This low-resistance state can be effectively disrupted by moving oxygen vacancies out of the Filament to reach high-resistance states.
Ming Liu - One of the best experts on this subject based on the ideXlab platform.
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Correlation analysis between the current fluctuation characteristics and the Conductive Filament morphology of HfO2-based memristor
Applied Physics Letters, 2017Co-Authors: Kang-sheng Yin, Shibing Long, Meiyun Zhang, Long Cheng, Ya-xiong Zhou, Zhuo-rui Wang, Kan-hao Xue, Ming LiuAbstract:Memristors are attracting considerable interest for their prospective applications in nonvolatile memory, neuromorphic computing, and in-memory computing. However, the nature of resistance switching is still under debate, and current fluctuation in memristors is one of the critical concerns for stable performance. In this work, random telegraph noise (RTN) as the indication of current instabilities in distinct resistance states of the Pt/Ti/HfO2/W memristor is thoroughly investigated. Standard two-level digital-like RTN, multilevel current instabilities with non-correlation/correlation defects, and irreversible current transitions are observed and analyzed. The dependence of RTN on the resistance and read bias reveals that the current fluctuation depends strongly on the morphology and evolution of the Conductive Filament composed of oxygen vacancies. Our results link the current fluctuation behaviors to the evolution of the Conductive Filament and will guide continuous optimization of memristive devices.
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Investigation on the Conductive Filament Growth Dynamics in Resistive Switching Memory via a Universal Monte Carlo Simulator
Scientific Reports, 2017Co-Authors: Yu Li, Jiao Teng, Hangbing Lv, Shibing Long, Jordi Suñé, Enrique Miranda, Meiyun Zhang, Qi Liu, Ming LiuAbstract:In resistive random access memories, modeling Conductive Filament growing dynamics is important to understand the switching mechanism and variability. In this paper, a universal Monte Carlo simulator is developed based on a cell switching model and a tunneling-based transport model. Driven by external electric field, the growing process of the nanoscale Filament occurring in the gap region is actually dominated by cells’ Conductive/insulating switching, modeled through a phenomenological physics-based probability function. The electric transport through the partially formed CF is considered as current tunneling in the framework of the Quantum Point Contact model, and the potential barrier is modulated during cells’ evolution. To demonstrate the validity and universality of our simulator, various operation schemes are simulated, with the simulated I − V characteristics well explaining experimental observations. Furthermore, the statistical analyses of simulation results in terms of Weibull distribution and conductance evolution also nicely track previous experimental results. Representing a simulation scale that links atomic-scale simulations to compact modeling, our simulator has the advantage of being much faster comparing with other atomic-scale models. Meanwhile, our simulator shows good universality since it can be applied to various operation signals, and also to different electrodes and dielectric layers dominated by different switching mechanisms.
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Resistive Switching Performance Improvement via Modulating Nanoscale Conductive Filament, Involving the Application of Two-Dimensional Layered Materials.
Small (Weinheim an der Bergstrasse Germany), 2017Co-Authors: Shibing Long, Qi Liu, Ming LiuAbstract:Reversible chemical and structural changes induced by ionic motion and reaction in response to electrical stimuli leads to resistive switching effects in metal-insulator-metal structures. Filamentary switching based on the formation and rupture of nanoscale Conductive Filament has been applied in non-volatile memory and volatile selector devices with low power consumption and fast switching speeds. Before the mass production of resistive switching devices, great efforts are still required to enable stable and reliable switching performances. The Conductive Filament, a bridge of microscopic metal-insulator-metal structure and macroscopic resistance states, plays an irreplaceable part in resistive switching behavior, as unreliable performance often originates from unstable Filament behavior. In this Review, departing from the Filamentary switching mechanism and the existing issues, recent advances of the switching performance improvement through the Conductive Filament modulation are discussed, in the sequence of material modulation, device structure design and switching operation scheme optimization. In particular, two-dimensional (2D) nanomaterials with excellent properties including and beyond graphene, are discussed with emphasis on performance improvement by their active roles as the switching layer, insertion layer, thin electrode, patterned electrode, and edge electrode, etc.
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anisotropic magnetoresistance of nano Conductive Filament in co hfo2 pt resistive switching memory
Nanoscale Research Letters, 2017Co-Authors: Yang Liu, Jiao Teng, Shibing Long, Meiyun Zhang, Qi Liu, Qixun Guo, Ming LiuAbstract:Conductive bridge random access memory (CBRAM) has been extensively studied as a next-generation non-volatile memory. The Conductive Filament (CF) shows rich physical effects such as conductance quantization and magnetic effect. But so far, the study of Filaments is not very sufficient. In this work, Co/HfO2/Pt CBRAM device with magnetic CF was designed and fabricated. By electrical manipulation with a partial-RESET method, we controlled the size of ferromagnetic metal Filament. The resistance-temperature characteristics of the ON-state after various partial-RESET behaviors have been studied. Using two kinds of magnetic measurement methods, we measured the anisotropic magnetoresistance (AMR) of the CF at different temperatures to reflect the magnetic structure characteristics. By rotating the direction of the magnetic field and by sweeping the magnitude, we obtained the spatial direction as well as the easy-axis of the CF. The results indicate that the easy-axis of the CF is along the direction perpendicular to the top electrode plane. The maximum magnetoresistance was found to appear when the angle between the direction of magnetic field and that of the electric current in the CF is about 30°, and this angle varies slightly with temperature, indicating that the current is tilted.
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justification and monte carlo simulation of microstructure evolution process of Conductive Filament in reset transition in cu hfo 2 pt rram
International Symposium on the Physical and Failure Analysis of Integrated Circuits, 2015Co-Authors: Meiyun Zhang, Shibing Long, Qi Liu, Guoming Wang, Haitao Sun, Ming LiuAbstract:We proposed a new statistical evaluation method to justify the microstructure evolution process of Conductive Filament (CF) in the reset operation of resistive switching memory (RRAM) according to the dependence of the Weibull slope of reset parameters on the CF size. We demonstrated that in Cu/HfO 2 /Pt device the CF can be controlled to be ruptured abruptly, which is more advantageous to the reliable operation of RRAM since the intermediate states are avoided. A Monte Carlo (MC) simulator based on the thermal dissolution model is conducted to further prove our experimental results.
Seong-geon Park - One of the best experts on this subject based on the ideXlab platform.
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First-principles investigation of the Conductive Filament configuration in rutile TiO 2-x ReRAM
MRS Proceedings, 2012Co-Authors: Liang Zhao, Seong-geon Park, Blanka Magyari-köpe, Yoshio NishiAbstract:ABSTRACTThe interactions and ordering of oxygen vacancies in rutile TiO2 were thoroughly investigated by density functional calculations to search for atomic configurations of the Conductive Filament. As random isolated vacancies could not support the low-resistance state conduction in TiO2 ReRAM, vacancy ordering was introduced in [110] and [001] directions of the lattice to study the electronic structures. The calculation results revealed that a di-vacancy chain in [001] direction makes the electrons delocalized in that direction, which is identified as a possible configuration of the Conductive Filament. This low-resistance state can be effectively disrupted by moving oxygen vacancies out of the Filament to reach high-resistance states.
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impact of oxygen vacancy ordering on the formation of a Conductive Filament in hbox tio _ 2 for resistive switching memory
IEEE Electron Device Letters, 2011Co-Authors: Seong-geon Park, Blanka Magyarikope, Yoshio NishiAbstract:The electronic properties of rutile TiO2 with an ordered arrangement of oxygen vacancies show a transition from a resistive to Conductive oxide as a function of vacancy ordering. Vacancy ordering along two different directions [110] and [001], studied by the density functional theory, predicts that the geometries in which the vacancy-to-vacancy interaction is the strongest, within the nearest neighbor coordination, are thermodynamically favorable and of technological importance. The oxygen vacancies induce several occupied defect states of Ti 3d character, and according to our model, the vacancies are the mediators of electron conduction, while the Conductive Filament is formed by Ti ions. We propose that the formation of these types of Conductive Filament is intrinsically connected to the observed defect-assisted tunneling processes and oxide breakdown issues.
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Impact of Oxygen Vacancy Ordering on the Formation of a Conductive Filament in $\hbox{TiO}_{2}$ for Resistive Switching Memory
IEEE Electron Device Letters, 2011Co-Authors: Seong-geon Park, Blanka Magyari-köpe, Yoshio NishiAbstract:The electronic properties of rutile TiO2 with an ordered arrangement of oxygen vacancies show a transition from a resistive to Conductive oxide as a function of vacancy ordering. Vacancy ordering along two different directions [110] and [001], studied by the density functional theory, predicts that the geometries in which the vacancy-to-vacancy interaction is the strongest, within the nearest neighbor coordination, are thermodynamically favorable and of technological importance. The oxygen vacancies induce several occupied defect states of Ti 3d character, and according to our model, the vacancies are the mediators of electron conduction, while the Conductive Filament is formed by Ti ions. We propose that the formation of these types of Conductive Filament is intrinsically connected to the observed defect-assisted tunneling processes and oxide breakdown issues.
Takeshi Takagi - One of the best experts on this subject based on the ideXlab platform.
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Comprehensive understanding of Conductive Filament characteristics and retention properties for highly reliable ReRAM
2013Co-Authors: S. Muraoka, Takeki Ninomiya, Koji Katayama, Ryutaro Yasuhara, Zhiqiang Wei, Takeshi TakagiAbstract:We have proposed a retention degradation model based on an oxygen diffusion and percolation path cut mechanism in a Filament of TaOx bipolar ReRAM. We have developed a new methodology for quantitating the Conductive Filament characteristics and have revealed that the retention property of ReRAMs can be explained in terms of Filament characteristics, including Filament size S, density of oxygen vacancies N(Vo), and density of residual oxygen N(Ox). We have improved the retention property of ReRAM under low current operation, by controlling these Filament characteristics.
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Conductive Filament scaling of rm tao _ rm x bipolar reram for improving data retention under low operation current
IEEE Transactions on Electron Devices, 2013Co-Authors: Takeki Ninomiya, Koji Katayama, Shunsaku Muraoka, Ryutaro Yasuhara, Z. Wei, Takeshi TakagiAbstract:The retention model of a bipolar ReRAM considering the percolative paths in a Conductive Filament is proposed. We demonstrate, for the first time, that the control of oxygen vacancy concentration in a Conductive Filament is the key for ensuring data retention including tail bits. To improve the retention property under low-current operation, the size of the Conductive Filament must be scaled down while keeping the density of oxygen vacancy high enough. Based on this concept, we demonstrate both low-current operation and sufficient retention results exceeding 500 h at 150°C, which correspond to more than 10 years at 85°C.
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Consideration of Conductive Filament for realization of low-current and highly-reliable TaO x ReRAM
2013 5th IEEE International Memory Workshop, 2013Co-Authors: Ryutaro Yasuhara, Takeki Ninomiya, Koji Katayama, Z. Wei, S. Muraoka, Takeshi TakagiAbstract:Characteristics and their origin of a Conductive Filament in TaOx ReRAM are investigated. The results of systematic experimentation demonstrate that the formation of a small Conductive Filament with high density of oxygen vacancies, achieved by controlling the oxygen content of the resistance-switching material and forming/set current, is the key to achieving low-current switching combined with long retention.
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Conductive Filament Scaling of ${\rm TaO}_{\rm x}$ Bipolar ReRAM for Improving Data Retention Under Low Operation Current
IEEE Transactions on Electron Devices, 2013Co-Authors: Takeki Ninomiya, Koji Katayama, Ryutaro Yasuhara, Z. Wei, S. Muraoka, Takeshi TakagiAbstract:The retention model of a bipolar ReRAM considering the percolative paths in a Conductive Filament is proposed. We demonstrate, for the first time, that the control of oxygen vacancy concentration in a Conductive Filament is the key for ensuring data retention including tail bits. To improve the retention property under low-current operation, the size of the Conductive Filament must be scaled down while keeping the density of oxygen vacancy high enough. Based on this concept, we demonstrate both low-current operation and sufficient retention results exceeding 500 h at 150°C, which correspond to more than 10 years at 85°C.
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Conductive Filament scaling of TaO x bipolar ReRAM for long retention with low current operation
2012 Symposium on VLSI Technology (VLSIT), 2012Co-Authors: Takeki Ninomiya, Koji Katayama, Ryutaro Yasuhara, Takeshi Takagi, Z. Wei, S. Muraoka, Yuichiro Ikeda, Ken Kawai, Y. Kato, Yoshio KawashimaAbstract:We demonstrate for the first time that the density of oxygen vacancy in a Conductive Filament plays a key role in ensuring data retention. We achieve very good retention results up to 100 hours at 150°C even under the low current operation due to the scaling of Conductive Filament size while retaining sufficiently high density of oxygen vacancy.
Blanka Magyari-köpe - One of the best experts on this subject based on the ideXlab platform.
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HfO2/Ti Interface Mediated Conductive Filament Formation in RRAM: An Ab Initio Study
IEEE Transactions on Electron Devices, 2018Co-Authors: Boubacar Traore, Blanka Magyari-köpe, Philippe Blaise, Benoit Sklenard, Elisa Vianello, Yoshio NishiAbstract:We address the role of the Ti/HfO2 interface on the Conductive Filament (CF) formation within the context of oxide-based resistive random access memories (OxRRAMs). We investigate oxygen defects formation and diffusion at the interface through ab initio calculations. The calculated diffusion energy barriers compare well with the available experimental data. Through the interface region charge analysis and the associated energies with O defect formation and migration into Ti, our results support a probable CF growth from the interface region toward the electron injecting electrode, which acts as a cathode. Hence, for a Ti/HfO2-based OxRRAM supported by the calculation results, we present a pertinent CF growth model by considering its earliest stages, which is relevant for device modeling.
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HfO 2 /Ti Interface Mediated Conductive Filament Formation in RRAM: An Ab Initio Study
IEEE Transactions on Electron Devices, 2018Co-Authors: Boubacar Traore, Blanka Magyari-köpe, Philippe Blaise, Benoit Sklenard, Elisa Vianello, Yoshio NishiAbstract:We address the role of the Ti/HfO2 interface on the Conductive Filament (CF) formation within the context of oxide-based resistive random access memories (OxRRAMs). We investigate oxygen defects formation and diffusion at the interface through ab initio calculations. The calculated diffusion energy barriers compare well with the available experimental data. Through the interface region charge analysis and the associated energies with O defect formation and migration into Ti, our results support a probable CF growth from the interface region toward the electron injecting electrode, which acts as a cathode. Hence, for a Ti/HfO2-based OxRRAM supported by the calculation results, we present a pertinent CF growth model by considering its earliest stages, which is relevant for device modeling.
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H-treatment impact on Conductive-Filament formation and stability in Ta2O5-based resistive-switching memory cells
Journal of Applied Physics, 2015Co-Authors: Ludovic Goux, Blanka Magyari-köpe, Yoshio Nishi, Ja-yong Kim, Augusto Redolfi, Malgorzata JurczakAbstract:In this article, we evidence the lower formation energy and improved stability of the Conductive Filament (CF) formed in TiN\Ta2O5\Ta resistive-switching memory cells treated in NH3 atmosphere at 400 °C. This annealing treatment results in (i) lower forming voltage, (ii) lower CF resistance, and (iii) longer retention lifetime of the oxygen-vacancy (Vo) chain constituting the CF. Atomistic insights into these processes are provided by ab initio calculations performed for hydrogen (H) species incorporated in non-stoichiometric Ta2O5 supercells: (i) Vo formation energy is reduced by the presence of H, (ii) Vo-chain CF conductivity is increased by Vo + OH complex formation, and (iii) Vo-chain retention is strengthened by the stable Vo + OH complex. As a result, efficient CF formation and excellent state stability are obtained after 15 days at 250 °C.
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First-principles investigation of the Conductive Filament configuration in rutile TiO 2-x ReRAM
MRS Proceedings, 2012Co-Authors: Liang Zhao, Seong-geon Park, Blanka Magyari-köpe, Yoshio NishiAbstract:ABSTRACTThe interactions and ordering of oxygen vacancies in rutile TiO2 were thoroughly investigated by density functional calculations to search for atomic configurations of the Conductive Filament. As random isolated vacancies could not support the low-resistance state conduction in TiO2 ReRAM, vacancy ordering was introduced in [110] and [001] directions of the lattice to study the electronic structures. The calculation results revealed that a di-vacancy chain in [001] direction makes the electrons delocalized in that direction, which is identified as a possible configuration of the Conductive Filament. This low-resistance state can be effectively disrupted by moving oxygen vacancies out of the Filament to reach high-resistance states.
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Impact of Oxygen Vacancy Ordering on the Formation of a Conductive Filament in $\hbox{TiO}_{2}$ for Resistive Switching Memory
IEEE Electron Device Letters, 2011Co-Authors: Seong-geon Park, Blanka Magyari-köpe, Yoshio NishiAbstract:The electronic properties of rutile TiO2 with an ordered arrangement of oxygen vacancies show a transition from a resistive to Conductive oxide as a function of vacancy ordering. Vacancy ordering along two different directions [110] and [001], studied by the density functional theory, predicts that the geometries in which the vacancy-to-vacancy interaction is the strongest, within the nearest neighbor coordination, are thermodynamically favorable and of technological importance. The oxygen vacancies induce several occupied defect states of Ti 3d character, and according to our model, the vacancies are the mediators of electron conduction, while the Conductive Filament is formed by Ti ions. We propose that the formation of these types of Conductive Filament is intrinsically connected to the observed defect-assisted tunneling processes and oxide breakdown issues.