In this study, the unipolar resistive switching （URS） and bipolar resistive switching （BRS） are demonstrated to be coexistent in the Ag/ZnO/Pt memory device, and both modes are observed to strongly depend on the p...In this study, the unipolar resistive switching （URS） and bipolar resistive switching （BRS） are demonstrated to be coexistent in the Ag/ZnO/Pt memory device, and both modes are observed to strongly depend on the polarity of forming voltage. The mechanisms of the URS and BRS behaviors could be attributed to the electric-field-induced migration of oxygen vacancies （Vo） and metal-Ag conducting filaments （CFs） respectively, which are confirmed by investigating the temperature dependences of low resistance states in both modes. Furthermore, we compare the resistive switching （RS） characteristics （e.g., forming and switching voltages, reset current and resistance states） between these two modes based on Vo- and Ag-CFs. The BRS mode shows better switching uniformity and lower power than the URS mode. Both of these modes exhibit good RS performances, including good retention, reliable cycling and high-speed switching. The result indicates that the coexistence of URS and BRS behaviors in a single device has great potential applications in future nonvolatile multi-level memory.展开更多
Unipolar memristive devices are an important kind of resistive switching devices. However, few circuit models of them have been proposed. In this paper, we propose the SPICE modeling of flux-controlled unipolar memris...Unipolar memristive devices are an important kind of resistive switching devices. However, few circuit models of them have been proposed. In this paper, we propose the SPICE modeling of flux-controlled unipolar memristive devices based on the memristance versus state map. Using our model, the flux thresholds, ON and OFF resistance, and compliance current can easily be set as model parameters. We simulate the model in HSPICE using model parameters abstracted from real devices, and the simulation results show that the proposed model caters to the real device data very well, thus demonstrating that the model is correct. Using the same modeling methodology, the SPICE model of charge-controlled unipolar memristive devices could also be developed. The proposed model could be used to model resistive memory cells, logical gates as well as synapses in artificial neural networks.展开更多
By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinu- soidal pulse width modulation （BSPWM） and unipolar double-frequency sinusoidal pulse width modulati...By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinu- soidal pulse width modulation （BSPWM） and unipolar double-frequency sinusoidal pulse width modulation （UDFSPWM） respectively, the performances of the two modulation strategies are analyzed in detail. The circuit parameters, used in this paper, are fixed. When the systems, modulated by BSPWM and UDFSPWM, have the same switching frequency, the stabil- ity boundaries of the two systems are the same. However, when the equivalent switching frequencies of the two systems are the same, the BSPWM modulated system is more stable than the UDFSPWM modulated system. In addition, a convenient method of establishing the discrete-time model of piecewise smooth system is presented. Finally, the analytical results are confirmed by circuit simulations and experimental measurements.展开更多
The identification of the switching location has been a key technology to tune the physical properties of unipolar resistive switching（RS） cells.Here we report the RS properties of Au/Ni O/Sr Ti O3（STO）/Pt memory ...The identification of the switching location has been a key technology to tune the physical properties of unipolar resistive switching（RS） cells.Here we report the RS properties of Au/Ni O/Sr Ti O3（STO）/Pt memory cells.The switching repeatability is closely related to the applied bias polarity,which is different from the scenario of the Au/STO/Pt cells reported in our previous researches.The high resistance in positive bias is greater than that in negative bias.The R（T）–R0I^2 R（T） plot of the on-state I–V curve shows a regular shape only with a slight bend and an abnormal shape with an abrupt increase and decrease under negative and positive bias,respectively.These comparative experimental results reveal that the conductance filament consisting of oxygen vacancies grows from the cathode to the anode.The spatial RS location is identified with the weaker part along the conductance filament length direction,which should be near the Ni O/STO interface and STO/Pt interface under positive and negative bias,respectively.展开更多
The alternation from bipolar to unipolar resistive switching is observed in perovskite La0.01Sr0.99TiO3 thin films. These two switching modes can be activated separately depending on the compliance current （Icomp） d...The alternation from bipolar to unipolar resistive switching is observed in perovskite La0.01Sr0.99TiO3 thin films. These two switching modes can be activated separately depending on the compliance current （Icomp） during the electroforming process： with a higher Icomp （5 mA） the unipolar resistance switching behavior is measured, while the bipolar resistance switching behavior is observed with a lower Icomp （1 mA）. On the basis of I–V characteristics, the switching mechanisms for the URS and BRS modes are considered as being a change in the Schottky-like barrier height and/or width at the Pt/La-SrTiO3 interface and the formation and disruption of conduction filaments, respectively.展开更多
Strategically designing the electrocatalytic system and cleverly inducing strain is an effective approach to balance the cost and activity of Pt-based electrocatalysts for industrial-scale hydrogen production.Herein,w...Strategically designing the electrocatalytic system and cleverly inducing strain is an effective approach to balance the cost and activity of Pt-based electrocatalysts for industrial-scale hydrogen production.Herein,we present a unipolar pulsed electrodeposition(UPED) strategy to induce strain in the Ni lattice by introducing trace amounts of Pt single atoms(SAs)(0.22 wt%).The overpotential decreased by 183 mV at 10 mA cm^(-2) in 1.0 M KOH after introducing trace amounts of Pt_(SAs).The industrial electrolyzer,assembled with Pt_(SAs)Ni cathode and a commercial NiFeO_(x) anode,requires a cell voltage of 1.90 V to attain 1 A cm^(-2) of current density and remains stable for 280 h,demonstrating significant potential for practical applications.Spherical aberration corrected scanning transmission electron microscopy(AC-STEM),X-ray absorption(XAS),and geometric phase analysis(GPA) indicate that the introduction of trace amounts of Pt SAs induces tensile strain in the Ni lattice,thereby altering the local electronic structure and coordination environment around cubic Ni for enhancing the water decomposition kinetics and fundamentally changing the reaction pathway.The doping-strain strategy showcases conformational relationships that could offer new ideas to construct efficient hydrogen evolution reaction(HER) electrocatalysts for industrial hydrogen production in the future.展开更多
目的探讨腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC)超声刀与单极电凝钩对T淋巴细胞亚群的影响。方法对50例LC分别采用超声刀(超声刀组,n=25)与单极电凝钩(单级电凝钩组,n=25)手术,术前半小时、术后1d、术后4 d分别从外周血中...目的探讨腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC)超声刀与单极电凝钩对T淋巴细胞亚群的影响。方法对50例LC分别采用超声刀(超声刀组,n=25)与单极电凝钩(单级电凝钩组,n=25)手术,术前半小时、术后1d、术后4 d分别从外周血中测定CD3、CD4及CD8淋巴细胞亚群水平,2组进行比较。结果术前半小时2组CD3、CD4、CD8及CD4/8CD无统计学差异(P>0.05);术后1 d 2组病人外周血T淋巴细胞亚群CD3、CD4、CD4/CD8下降、CD8上升,电凝钩组CD3、CD4、CD4/CD8显著低于超声刀组(P<0.05),电凝钩组CD8显著高于超声刀组(P<0.05);术后4 d 2组病人外周血T淋巴细胞亚群均接近正常范围。结论LC使用超声刀比单极电凝钩对机体的免疫功能的影响较小。展开更多
基金Project supported by the National Natural Science Foundation of China for Excellent Young Scholars(Grant No.51422201)the National Natural Science Foundation of China(Grant Nos.51172041,51372035,11304035,61574031,and 61404026)+4 种基金the National Basic Research Program of China(Grant No.2012CB933703)the"111"Project,China(Grant No.B13013)the Fund from Jilin Province,China(Grant Nos.20140520106JH and 20140201008GX)the Research Fund for the Doctoral Program of Higher Education,China(Grant No.20130043110004)the Fundamental Research Funds for the Central Universities,China(Grant Nos.2412015KJ008 and 2412016KJ003)
文摘In this study, the unipolar resistive switching （URS） and bipolar resistive switching （BRS） are demonstrated to be coexistent in the Ag/ZnO/Pt memory device, and both modes are observed to strongly depend on the polarity of forming voltage. The mechanisms of the URS and BRS behaviors could be attributed to the electric-field-induced migration of oxygen vacancies （Vo） and metal-Ag conducting filaments （CFs） respectively, which are confirmed by investigating the temperature dependences of low resistance states in both modes. Furthermore, we compare the resistive switching （RS） characteristics （e.g., forming and switching voltages, reset current and resistance states） between these two modes based on Vo- and Ag-CFs. The BRS mode shows better switching uniformity and lower power than the URS mode. Both of these modes exhibit good RS performances, including good retention, reliable cycling and high-speed switching. The result indicates that the coexistence of URS and BRS behaviors in a single device has great potential applications in future nonvolatile multi-level memory.
基金the National Natural Science Foundation of China(Grant Nos.60921062,61003082,and 61272146)
文摘Unipolar memristive devices are an important kind of resistive switching devices. However, few circuit models of them have been proposed. In this paper, we propose the SPICE modeling of flux-controlled unipolar memristive devices based on the memristance versus state map. Using our model, the flux thresholds, ON and OFF resistance, and compliance current can easily be set as model parameters. We simulate the model in HSPICE using model parameters abstracted from real devices, and the simulation results show that the proposed model caters to the real device data very well, thus demonstrating that the model is correct. Using the same modeling methodology, the SPICE model of charge-controlled unipolar memristive devices could also be developed. The proposed model could be used to model resistive memory cells, logical gates as well as synapses in artificial neural networks.
基金supported by the National Natural Science Foundation of China (Grant No. 51277146)the Foundation of Delta Science,Technologythe Education Development Program for Power Electronics (Grant No. DREG2011003)
文摘By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinu- soidal pulse width modulation （BSPWM） and unipolar double-frequency sinusoidal pulse width modulation （UDFSPWM） respectively, the performances of the two modulation strategies are analyzed in detail. The circuit parameters, used in this paper, are fixed. When the systems, modulated by BSPWM and UDFSPWM, have the same switching frequency, the stabil- ity boundaries of the two systems are the same. However, when the equivalent switching frequencies of the two systems are the same, the BSPWM modulated system is more stable than the UDFSPWM modulated system. In addition, a convenient method of establishing the discrete-time model of piecewise smooth system is presented. Finally, the analytical results are confirmed by circuit simulations and experimental measurements.
基金Project supported by the National Natural Science Foundation of China(Grant No.11404093)the Foundation of Henan Provincial Science and Technology Department,China(Grant No.132102210258)+1 种基金the Research Funding from Henan Province,China(Grant Nos.15A140001,2015GGJS-021,and 17HASTIT014)the Henan University Emerging Cross and Characteristic Discipline Cultivation Program,China(Grant No.xxjc20140016)
文摘The identification of the switching location has been a key technology to tune the physical properties of unipolar resistive switching（RS） cells.Here we report the RS properties of Au/Ni O/Sr Ti O3（STO）/Pt memory cells.The switching repeatability is closely related to the applied bias polarity,which is different from the scenario of the Au/STO/Pt cells reported in our previous researches.The high resistance in positive bias is greater than that in negative bias.The R（T）–R0I^2 R（T） plot of the on-state I–V curve shows a regular shape only with a slight bend and an abnormal shape with an abrupt increase and decrease under negative and positive bias,respectively.These comparative experimental results reveal that the conductance filament consisting of oxygen vacancies grows from the cathode to the anode.The spatial RS location is identified with the weaker part along the conductance filament length direction,which should be near the Ni O/STO interface and STO/Pt interface under positive and negative bias,respectively.
基金Project supported by the Key Projects of the National Natural Science Foundation of China(Grant No.11032010)the National Natural Science Foundation of China(Grant Nos.51072171,61274107,61176093,and 11275163)+4 种基金the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT1080)the National Basic Rearch Program of China(Grant No.2012CB326404)the Key Projects of Scientific Research Fund of Hunan Provincial Education Department,China(Grant No.12A129)the Doctoral Program of Higher Education of China(Grant No.20104301110001)the Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province,China
文摘The alternation from bipolar to unipolar resistive switching is observed in perovskite La0.01Sr0.99TiO3 thin films. These two switching modes can be activated separately depending on the compliance current （Icomp） during the electroforming process： with a higher Icomp （5 mA） the unipolar resistance switching behavior is measured, while the bipolar resistance switching behavior is observed with a lower Icomp （1 mA）. On the basis of I–V characteristics, the switching mechanisms for the URS and BRS modes are considered as being a change in the Schottky-like barrier height and/or width at the Pt/La-SrTiO3 interface and the formation and disruption of conduction filaments, respectively.
基金National Natural Science Foundation of China (grants U22A20418, 22075196, and 21878204)Research Project Supported by Shanxi Scholarship Council of China (2022-050)。
文摘Strategically designing the electrocatalytic system and cleverly inducing strain is an effective approach to balance the cost and activity of Pt-based electrocatalysts for industrial-scale hydrogen production.Herein,we present a unipolar pulsed electrodeposition(UPED) strategy to induce strain in the Ni lattice by introducing trace amounts of Pt single atoms(SAs)(0.22 wt%).The overpotential decreased by 183 mV at 10 mA cm^(-2) in 1.0 M KOH after introducing trace amounts of Pt_(SAs).The industrial electrolyzer,assembled with Pt_(SAs)Ni cathode and a commercial NiFeO_(x) anode,requires a cell voltage of 1.90 V to attain 1 A cm^(-2) of current density and remains stable for 280 h,demonstrating significant potential for practical applications.Spherical aberration corrected scanning transmission electron microscopy(AC-STEM),X-ray absorption(XAS),and geometric phase analysis(GPA) indicate that the introduction of trace amounts of Pt SAs induces tensile strain in the Ni lattice,thereby altering the local electronic structure and coordination environment around cubic Ni for enhancing the water decomposition kinetics and fundamentally changing the reaction pathway.The doping-strain strategy showcases conformational relationships that could offer new ideas to construct efficient hydrogen evolution reaction(HER) electrocatalysts for industrial hydrogen production in the future.
文摘目的探讨腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC)超声刀与单极电凝钩对T淋巴细胞亚群的影响。方法对50例LC分别采用超声刀(超声刀组,n=25)与单极电凝钩(单级电凝钩组,n=25)手术,术前半小时、术后1d、术后4 d分别从外周血中测定CD3、CD4及CD8淋巴细胞亚群水平,2组进行比较。结果术前半小时2组CD3、CD4、CD8及CD4/8CD无统计学差异(P>0.05);术后1 d 2组病人外周血T淋巴细胞亚群CD3、CD4、CD4/CD8下降、CD8上升,电凝钩组CD3、CD4、CD4/CD8显著低于超声刀组(P<0.05),电凝钩组CD8显著高于超声刀组(P<0.05);术后4 d 2组病人外周血T淋巴细胞亚群均接近正常范围。结论LC使用超声刀比单极电凝钩对机体的免疫功能的影响较小。
