The spike-response model(SRM)describes the adaptive behaviors of a biological neuron in response to repeated or prolonged stimulation,so that SRM neurons can avoid information overload and support neural networks for ...The spike-response model(SRM)describes the adaptive behaviors of a biological neuron in response to repeated or prolonged stimulation,so that SRM neurons can avoid information overload and support neural networks for competitive learning.In this work,an artificial SRM neuron with the leaky integrate-and-fire(LIF)functions and the adaptive threshold is firstly implemented by the volatile memris-tive device of Pt/NbO_(x)/TiN.By modulating the volatile speed of the device,the threshold of the SRM neuron is adjusted to achieve the adaptive behaviors,such as the refractory period and the lateral inhi-bition.To demonstrate the function of the SRM neuron,a spiking neu-ral network(SNN)is constructed with the SRM neurons and trained by the unsupervised learning rule,which successfully classifies letters with noises,while a similar SNN with LIF neurons fails.This work demonstrates that the SRM neuron not only emulates the adaptive behaviors of a biological neuron,but also enriches the functionality and unleashes the computational power of SNNs.展开更多
The electrophysical and structural characteristics of bismuth titanate oxides of a number of phases of solid solutions of the Aurivillius phases Bi_(7−2x)Nd_(2x)Ti_(4)NbO_(21)(x=0.0,0.2,0.4,0.6,0.8,1.0)having a layere...The electrophysical and structural characteristics of bismuth titanate oxides of a number of phases of solid solutions of the Aurivillius phases Bi_(7−2x)Nd_(2x)Ti_(4)NbO_(21)(x=0.0,0.2,0.4,0.6,0.8,1.0)having a layered structure of the perovskite type have been investigated.According to the XRD data,all studied compounds are single-phase and have a mixed-layer structure of Aurivillius phases(m=2.5)with a rhombic crystal lattice(space group I2cm,Z=2).A relationship has been established between changes in the chemical composition of solid solutions and orthorhombic and tetragonal distortions of perovskite-like layers.The temperature dependences of the relative permittivityε/ε_(o)(T)are measured.It was found that the change in the phase transition temperature-Curie temperature T_(C)synthesized Aurivillius phases Bi_(7−x)Nd_(2x)Ti_(4)NbO_(21)(x=0.0,0.2,0.4,0.6,0.8,1.0)has a close to linear dependence on the change in the parameter x.The activation energies of charge carriers in different temperature ranges were calculated.It was found that three clearly defined temperature ranges with different activation energies can be distinguished,which is associated with the different nature of charge carriers in the studied solid solutions of the perovskite type.The effect of substitution of Nd^(3+)ions for Bi3+ions is investigated.展开更多
Spiking neural network(SNN)consisting of memristor-based artificial neurons and synapses has emerged as a compact and energy-efficient hardware solution for spatiotemporal information processing.However,it is challeng...Spiking neural network(SNN)consisting of memristor-based artificial neurons and synapses has emerged as a compact and energy-efficient hardware solution for spatiotemporal information processing.However,it is challenging to develop memristive neurons and synapses based on the same material system because the required resistive switching(RS)characteristics are different.Here,it is shown that SrFeO_(x)(SFO),an intriguing material system exhibiting topotactic phase transformation between insulating brownmillerite(BM)SrFeO_(2).5 phase and conductive perovskite(PV)SrFeO_(3) phase,can be engineered into both neuronal and synaptic devices.Using a BM-SFO single layer as the RS medium,the Au/BM-SFO/SrRuO_(3)(SRO)memristor exhibits nonvolatile RS behavior originating from the formation/rupture of PV-SFO filaments in the BM-SFO matrix.By contrast,using a PV-SFO(matrix)/BM-SFO(interfacial layer)bilayer as the RS medium,the Au/PV-SFO/BM-SFO/SRO memristor exhibits volatile RS behavior originating from the interfacial BM-PV phase transformation.Synaptic and neuronal characteristics are further demonstrated in the Au/BM-SFO/SRO and Au/PV-SFO/BM-SFO/SRO memristors,respectively.Using the SFO-based synapses and neurons,fully memristive SNNs are constructed by simulation,which show good performance on unsupervised image recognition.Our study suggests that SFO is a versatile material platform on which both neuronal and synaptic devices can be developed for constructing fully memristive SNNs.展开更多
A library of ceramic compounds based on the lead-free(K_(x)Na_(1-x))1-yLiy(Nb1-zTaz)O_(3)solid solution has been synthesized and characterized using high-throughput experimentation(HTE)method.The phase space previousl...A library of ceramic compounds based on the lead-free(K_(x)Na_(1-x))1-yLiy(Nb1-zTaz)O_(3)solid solution has been synthesized and characterized using high-throughput experimentation(HTE)method.The phase space previously reported by Saito and Takao has been expanded to{{x,0.1,1.0},{y,0,0.1},{z,0,0.2}},and new phase boundaries are observed.The relative density values show that with the appropriate sintering temperature,~92%of the theoretical density can be reached.The relative permittivity values show that with increasing amount of K+and Ta5+,the dielectric constant values increase.The effect of density on the dielectric constant values is however minimal.Resistivity values ranging from 109 to 1013Ω·cm are obtained for the samples.The piezoelectric charge coefficient values for selected compositions show that higher values are obtained close to the phase boundaries rather than away from them.The properties for the ceramic library using the HTE method are generally 15%-20%less than from the conventional method.This method is therefore more suited for screening of sample compositions than for producing samples with high piezoelectric properties.展开更多
AgNbO_(3) is an antiferroelectric (AFE) material with double hysteresis loop. Both the antiferroelectricityand ferroelectricity can be enhanced by doping. Herein, the ferroelectricity of AgNbO_(3) ceramics wasenhanced...AgNbO_(3) is an antiferroelectric (AFE) material with double hysteresis loop. Both the antiferroelectricityand ferroelectricity can be enhanced by doping. Herein, the ferroelectricity of AgNbO_(3) ceramics wasenhanced via K-doping and the phase diagram of the (Ag_(1-x)K_(x))NbO_(3) ceramics was upgraded. In details,(Ag_(1-x)K_(x))NbO_(3) ceramics are ferrielectric (FIE) M1 phase as x=5.00-5.50 mol% and ferroelectric (FE) Ophase as x=5.75-6.00 mol% before poling, and FE O phase as x=5.00-6.00 mol% after poling at roomtemperature. With increasing temperature, (Ag_(1-x)K_(x))NbO_(3) ceramics show the phase evolutions from FIEM1, AFE M2 to paraelectric (PE) T phase at x=5.00-5.50 mol% and from FE O, FE T to PE T phase at x=5.75-6.00 mol% before poling, and from FE O, FE T to PE T phase at x=5.00-6.00 mol% after poling.High d33 values of 180 pC/N and 285 pC/N are obtained at the FE O-FE T and FE T-PE T phase boundaries.This work sheds light on a novel and promising lead-free piezoelectric system.展开更多
基金This work is supported by the National Key Research and Develop-ment Program of China(Grant no.2018YFE0203802).
文摘The spike-response model(SRM)describes the adaptive behaviors of a biological neuron in response to repeated or prolonged stimulation,so that SRM neurons can avoid information overload and support neural networks for competitive learning.In this work,an artificial SRM neuron with the leaky integrate-and-fire(LIF)functions and the adaptive threshold is firstly implemented by the volatile memris-tive device of Pt/NbO_(x)/TiN.By modulating the volatile speed of the device,the threshold of the SRM neuron is adjusted to achieve the adaptive behaviors,such as the refractory period and the lateral inhi-bition.To demonstrate the function of the SRM neuron,a spiking neu-ral network(SNN)is constructed with the SRM neurons and trained by the unsupervised learning rule,which successfully classifies letters with noises,while a similar SNN with LIF neurons fails.This work demonstrates that the SRM neuron not only emulates the adaptive behaviors of a biological neuron,but also enriches the functionality and unleashes the computational power of SNNs.
基金The study was financially supported by the Ministry of Science and Higher Education of the Russian Federation[State task in the field of scientific activity,scientific project No.0852-2020-0032(BAS0110/20-3-08IF)].
文摘The electrophysical and structural characteristics of bismuth titanate oxides of a number of phases of solid solutions of the Aurivillius phases Bi_(7−2x)Nd_(2x)Ti_(4)NbO_(21)(x=0.0,0.2,0.4,0.6,0.8,1.0)having a layered structure of the perovskite type have been investigated.According to the XRD data,all studied compounds are single-phase and have a mixed-layer structure of Aurivillius phases(m=2.5)with a rhombic crystal lattice(space group I2cm,Z=2).A relationship has been established between changes in the chemical composition of solid solutions and orthorhombic and tetragonal distortions of perovskite-like layers.The temperature dependences of the relative permittivityε/ε_(o)(T)are measured.It was found that the change in the phase transition temperature-Curie temperature T_(C)synthesized Aurivillius phases Bi_(7−x)Nd_(2x)Ti_(4)NbO_(21)(x=0.0,0.2,0.4,0.6,0.8,1.0)has a close to linear dependence on the change in the parameter x.The activation energies of charge carriers in different temperature ranges were calculated.It was found that three clearly defined temperature ranges with different activation energies can be distinguished,which is associated with the different nature of charge carriers in the studied solid solutions of the perovskite type.The effect of substitution of Nd^(3+)ions for Bi3+ions is investigated.
基金The authors would like to thank the National Natural Science Foundation of China(Nos.92163210,U1932125,52172143)Science and Technology Program of Guangzhou(No.2019050001)Natural Science Foundation of Guangdong Province(No.2020A1515010996).
文摘Spiking neural network(SNN)consisting of memristor-based artificial neurons and synapses has emerged as a compact and energy-efficient hardware solution for spatiotemporal information processing.However,it is challenging to develop memristive neurons and synapses based on the same material system because the required resistive switching(RS)characteristics are different.Here,it is shown that SrFeO_(x)(SFO),an intriguing material system exhibiting topotactic phase transformation between insulating brownmillerite(BM)SrFeO_(2).5 phase and conductive perovskite(PV)SrFeO_(3) phase,can be engineered into both neuronal and synaptic devices.Using a BM-SFO single layer as the RS medium,the Au/BM-SFO/SrRuO_(3)(SRO)memristor exhibits nonvolatile RS behavior originating from the formation/rupture of PV-SFO filaments in the BM-SFO matrix.By contrast,using a PV-SFO(matrix)/BM-SFO(interfacial layer)bilayer as the RS medium,the Au/PV-SFO/BM-SFO/SRO memristor exhibits volatile RS behavior originating from the interfacial BM-PV phase transformation.Synaptic and neuronal characteristics are further demonstrated in the Au/BM-SFO/SRO and Au/PV-SFO/BM-SFO/SRO memristors,respectively.Using the SFO-based synapses and neurons,fully memristive SNNs are constructed by simulation,which show good performance on unsupervised image recognition.Our study suggests that SFO is a versatile material platform on which both neuronal and synaptic devices can be developed for constructing fully memristive SNNs.
基金The research leading to these results has received financial support from the Deutsche Forschungs Gemeinschaft(DFG)under Grant No.SCHN 372/16:1-2.
文摘A library of ceramic compounds based on the lead-free(K_(x)Na_(1-x))1-yLiy(Nb1-zTaz)O_(3)solid solution has been synthesized and characterized using high-throughput experimentation(HTE)method.The phase space previously reported by Saito and Takao has been expanded to{{x,0.1,1.0},{y,0,0.1},{z,0,0.2}},and new phase boundaries are observed.The relative density values show that with the appropriate sintering temperature,~92%of the theoretical density can be reached.The relative permittivity values show that with increasing amount of K+and Ta5+,the dielectric constant values increase.The effect of density on the dielectric constant values is however minimal.Resistivity values ranging from 109 to 1013Ω·cm are obtained for the samples.The piezoelectric charge coefficient values for selected compositions show that higher values are obtained close to the phase boundaries rather than away from them.The properties for the ceramic library using the HTE method are generally 15%-20%less than from the conventional method.This method is therefore more suited for screening of sample compositions than for producing samples with high piezoelectric properties.
基金This work was supported by the National Natural Science Foun-dation of China(No.51802068 and No.52073144)the Natural Sci-ence Foundation of Hebei Province,China(No.E2021201044)+4 种基金the Advanced Talents Incubation Program of the Hebei University,China(No.801260201180)the Natural Science Foundation of Jiangsu Province,China(No.BK20201301)the State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(No.KF202005 and No.KF202114)China Postdoctoral Science Foun-dation(No.2021M692491)Guangdong Basic and Applied Basic Research Foundation(No.2020A1515110251).
文摘AgNbO_(3) is an antiferroelectric (AFE) material with double hysteresis loop. Both the antiferroelectricityand ferroelectricity can be enhanced by doping. Herein, the ferroelectricity of AgNbO_(3) ceramics wasenhanced via K-doping and the phase diagram of the (Ag_(1-x)K_(x))NbO_(3) ceramics was upgraded. In details,(Ag_(1-x)K_(x))NbO_(3) ceramics are ferrielectric (FIE) M1 phase as x=5.00-5.50 mol% and ferroelectric (FE) Ophase as x=5.75-6.00 mol% before poling, and FE O phase as x=5.00-6.00 mol% after poling at roomtemperature. With increasing temperature, (Ag_(1-x)K_(x))NbO_(3) ceramics show the phase evolutions from FIEM1, AFE M2 to paraelectric (PE) T phase at x=5.00-5.50 mol% and from FE O, FE T to PE T phase at x=5.75-6.00 mol% before poling, and from FE O, FE T to PE T phase at x=5.00-6.00 mol% after poling.High d33 values of 180 pC/N and 285 pC/N are obtained at the FE O-FE T and FE T-PE T phase boundaries.This work sheds light on a novel and promising lead-free piezoelectric system.
