The interface with a pinned dipole within the composite barrier in a ferroelectric tunnel junction（FTJ） with symmetric electrodes is investigated.Different from the detrimental effect of the interface between the el...The interface with a pinned dipole within the composite barrier in a ferroelectric tunnel junction（FTJ） with symmetric electrodes is investigated.Different from the detrimental effect of the interface between the electrode and barrier in previous studies,the existence of an interface between the dielectric SrTiO_3 slab and ferroelectric BaTiO_3 slab in FTJs will enhance the tunneling electroresistance（TER） effect.Specifically,the interface with a lower dielectric constant and larger polarization pointing to the ferroelectric slab favors the increase of TER ratio.Therefore,interface control of high performance FTJ can be achieved.展开更多
Orientation anisotropy is a well-known essential character for polarization characteristics of ferroelectric materials,which has been widely investigated in conventional ferroelectric random access memories.In this wo...Orientation anisotropy is a well-known essential character for polarization characteristics of ferroelectric materials,which has been widely investigated in conventional ferroelectric random access memories.In this work,we study the effects of orientation on the tunneling electroresistance(TER)of ferroelectric tunnel junctions(FTJs).Rhombohedral Pb(Zr_(0.7),Ti_(0.3))O_(3)(PZT)that has the polar axis along the(111)orientation is adopted as potential barriers and two kinds of FTJs that are composed of(001)-and(II1)-oriented PZT barriers and Nb:SrTiO_(3)(Nb:STO)electrodes,respectively,are fabricated.The(111)-oriented P1PZT/Nb:STO FTJ exhibits a giant ON/OFFratio of~1.9×10^(5),about 30 times that of the(001)-oriented device,due to the lowered PZT barrier in the ON state and the widen Schottky barrier in the OFF state based on current and capacitance analyses.In addition,compared to the(001)-oriented device,the(111)-oriented FTJ shows a sharper and faster switching between the ON and OFF states according to the nucleation-limited-switching dynamics model,giving rise to good linearity in memristive behaviors for synaptic plasticity and reliable retention and endurance properties for the resistance switching.The improved TER properties are ascribed to larger effective polarizations and 180°switching in the(111)-oriented PZT barrier.These results facilitate the design and fabrication of high-performance FTJ devices with the optimization of crystallographic orientation and polarization switching characteristics.展开更多
Ferroelectric tunnel junction(FTJ)has attracted considerable attention for its potential applications in nonvolatile memory and neuromorphic computing.However,the experimental exploration of FTJs with high ON/OFF rati...Ferroelectric tunnel junction(FTJ)has attracted considerable attention for its potential applications in nonvolatile memory and neuromorphic computing.However,the experimental exploration of FTJs with high ON/OFF ratios is a challenging task due to the vast search space comprising of ferroelectric and electrode materials,fabrication methods and conditions and so on.Here,machine learning(ML)is demonstrated to be an effective tool to guide the experimental search of FTJs with high ON/OFF ratios.A dataset consisting of 152 FTJ samples with nine features and one target attribute(i.e.,ON/OFF ratio)is established for ML modeling.Among various ML models,the gradient boosting classification model achieves the highest prediction accuracy.Combining the feature importance analysis based on this model with the association rule mining,it is extracted that the utilizations of{graphene/graphite(Gra)(top),LaNiO_(3)(LNO)(bottom)}and{Gra(top),Ca_(0.96)Ce_(0.04)MnO_(3)(CCMO)(bottom)}electrode pairs are likely to result in high ON/OFF ratios in FTJs.Moreover,two previously unexplored FTJs:Gra/BaTiO_(3)(BTO)/LNO and Gra/BTO/CCMO,are predicted to achieve ON/OFF ratios higher than 1000.Guided by the ML predictions,the Gra/BTO/LNO and Gra/BTO/CCMO FTJs are experimentally fabricated,which unsurprisingly exhibit≥1000 ON/OFF ratios(~8540 and~7890,respectively).This study demonstrates a new paradigm of developing high-performance FTJs by using ML.展开更多
The multiple ferroelectric polarization tuned by external electric field could be used to simulate the biological synaptic weight. Ferroelectric synaptic devices have two advantages compared with other reported ones: ...The multiple ferroelectric polarization tuned by external electric field could be used to simulate the biological synaptic weight. Ferroelectric synaptic devices have two advantages compared with other reported ones: One is that the intrinsic switching of ferroelectric domains without invoking of defect migration as in resistive oxides, contributes reliable performance in these ferroelectric synapses. Another tremendous advantage is the extremely low energy consumption because the ferroelectric polarization is manipulated by electric field which eliminates the Joule heating by current as in magnetic and phase change memories. Ferroelectric synapses have potential for the construction of low-energy and effective brain-like intelligent networks. Here we summarize recent pioneering work of ferroelectric synapses involving the structure of ferroelectric tunnel junctions (FTJs), ferroelectric diodes (FDs), and ferroelectric field effect transistors (FeFETs), respectively, and shed light on future work needed to accelerate their application for efficient neural network.展开更多
Modulation between optical and ferroelectric properties was realized in a lateral structured ferroelectric CuInP_(2)S_(6)(CIPS)/semiconductor MoS_(2) van der Waals heterojunction.The ferroelectric hysteresis loop area...Modulation between optical and ferroelectric properties was realized in a lateral structured ferroelectric CuInP_(2)S_(6)(CIPS)/semiconductor MoS_(2) van der Waals heterojunction.The ferroelectric hysteresis loop area was modulated by the optical field.Two types of photodetection properties can be realized in a device by changing the ON and OFF states of the ferroelectric layer.The device was used as a photodetector in the OFF state but not in the ON state.The higher tunnelling electroresistance(~1.4×10^(4))in a lateral structured ferroelectric tunnelling junction was crucial,and it was analyzed and modulated by the barrier height and width of the ferroelectric CIPS/semiconductor MoS_(2) Schottky junction.The new parameter of the ferroelectric hysteresis loop area as a function of light intensity was introduced to analyze the relationship between the ferroelectric and photodetection properties.The proposed device has potential application as an optoelectronic sensory cell in the biological nervous system or as a new type of photodetector.展开更多
Ferroelectric tunnel junctions(FTJs)as the artificial synaptic devices have been considered promising for constructing brain-inspired neuromorphic computing systems.However,the memristive synapses based on the flexibl...Ferroelectric tunnel junctions(FTJs)as the artificial synaptic devices have been considered promising for constructing brain-inspired neuromorphic computing systems.However,the memristive synapses based on the flexible FTJs have been rarely studied.Here,we report a flexible FTJ memristor grown on a mica substrate,which consists of an ultrathin ferroelectric barrier of BiFeO_(3),a semiconducting layer of ZnO,and an electrode of SrRuO_(3).The obtained flexible FTJ memristor exhibits stable voltage-tuned multistates,and the resistive switchings are robust after 10^(3) bending cycles.The capability of the FTJ as a flexible synaptic device is demonstrated by the functionality of the spike-timing-dependent plasticity with bending,and the accurate conductance manipulation with small nonlinearity(-0.24)and low cycle-to-cycle variation(1.77%)is also realized.Especially,artificial neural network simulations based on experimental device behaviors reveal that the high recognition accuracies up to 92.8%and 86.2%are obtained for handwritten digits and images,respectively,which are close to the performances for ideal memristors.This work highlights the potential applications of FTJ as flexible electronics for data storage and processing.展开更多
The emergence of data-centric applications such as artificial intelligence(AI),machine learning,and the Internet of Things(IoT),has promoted surges in demand for storage memories with high operating speed and nonvolat...The emergence of data-centric applications such as artificial intelligence(AI),machine learning,and the Internet of Things(IoT),has promoted surges in demand for storage memories with high operating speed and nonvolatile characteristics.HfO_(2)-based ferroelectric memory technologies,which emerge as a promising alternative,have attracted considerable attention due to their high performance,energy efficiency,and full compatibility with the standard complementary metal-oxide-semiconductors(CMOS)process.These nonvolatile storage elements,such as ferroelectric random access memory(FeRAM),ferroelectric field-effect transistors(FeFETs),and ferroelectric tunnel junctions(FTJs),possess different data access mechanisms,individual merits,and specific application boundaries in next-generation memories or even beyond von Neumann architecture.This paper provides an overview of ferroelectric HfO2 memory technologies,addresses the current challenges,and offers insights into future research directions and prospects.展开更多
Two-dimensional(2D)ferroelectric(FE)materials with relatively low switching barrier and large polarization are promising candidates for next-generation miniaturized nonvolatile memory devices.Herein,we screen out 39 n...Two-dimensional(2D)ferroelectric(FE)materials with relatively low switching barrier and large polarization are promising candidates for next-generation miniaturized nonvolatile memory devices.Herein,we screen out 39 new 2D ferroelectric materials,MX(M:Group III-V elements;X:Group V-VII elements),in three phosphorus-analogue phases including black phosphorene-likeα-phase,blue phosphorus-likeβ-phase,and GeSe-likeγ-phase using high-throughput calculations.Seven materials(α-SbP,γ-AsP,etc.)exhibit FE switching barriers lower than 0.3 eV/f.u.,ferroelectric polarization larger than 2×10^(−10)C/m,and high thermodynamic stability with energy above hull smaller than 0.2 eV/atom.We find that the larger the electronegativity difference between M and X,the larger the ferroelectric polarization.Moreover,larger electronegativity differences result in lower in-plane piezoelectric stress tensor(e11)for MX consisting of Group IV and VI elements and larger e11 for those consisting of Group V elements.Further calculations predict a giant tunneling electroresistance in ferroelectric tunnel junctionα-Sb(Sn)P/α-SbP/α-Sb(Te)P(1.26×104%)and large piezoelectric strain coefficient inα-SnTe(396 pm/V),providing great opportunities to the design of non-volatile resistive memories,and high-performance piezoelectric devices.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11274054)the Open Project of Jiangsu Provincial Laboratory of Advanced Functional Materials,China(Grant No.12KFJJ005)
文摘The interface with a pinned dipole within the composite barrier in a ferroelectric tunnel junction（FTJ） with symmetric electrodes is investigated.Different from the detrimental effect of the interface between the electrode and barrier in previous studies,the existence of an interface between the dielectric SrTiO_3 slab and ferroelectric BaTiO_3 slab in FTJs will enhance the tunneling electroresistance（TER） effect.Specifically,the interface with a lower dielectric constant and larger polarization pointing to the ferroelectric slab favors the increase of TER ratio.Therefore,interface control of high performance FTJ can be achieved.
基金sponsored by the National Natural Science Foundation of China(No.52372113).
文摘Orientation anisotropy is a well-known essential character for polarization characteristics of ferroelectric materials,which has been widely investigated in conventional ferroelectric random access memories.In this work,we study the effects of orientation on the tunneling electroresistance(TER)of ferroelectric tunnel junctions(FTJs).Rhombohedral Pb(Zr_(0.7),Ti_(0.3))O_(3)(PZT)that has the polar axis along the(111)orientation is adopted as potential barriers and two kinds of FTJs that are composed of(001)-and(II1)-oriented PZT barriers and Nb:SrTiO_(3)(Nb:STO)electrodes,respectively,are fabricated.The(111)-oriented P1PZT/Nb:STO FTJ exhibits a giant ON/OFFratio of~1.9×10^(5),about 30 times that of the(001)-oriented device,due to the lowered PZT barrier in the ON state and the widen Schottky barrier in the OFF state based on current and capacitance analyses.In addition,compared to the(001)-oriented device,the(111)-oriented FTJ shows a sharper and faster switching between the ON and OFF states according to the nucleation-limited-switching dynamics model,giving rise to good linearity in memristive behaviors for synaptic plasticity and reliable retention and endurance properties for the resistance switching.The improved TER properties are ascribed to larger effective polarizations and 180°switching in the(111)-oriented PZT barrier.These results facilitate the design and fabrication of high-performance FTJ devices with the optimization of crystallographic orientation and polarization switching characteristics.
基金The authors would like to thank the National Natural Science Foundation of China(Nos.92163210,U1932125,52172143,12174347,61874158 and 92164109)Science and Technology Program of GuangZhou(No.2019050001)Natural Science of Guangdong Province(No.2020A1515010996).
文摘Ferroelectric tunnel junction(FTJ)has attracted considerable attention for its potential applications in nonvolatile memory and neuromorphic computing.However,the experimental exploration of FTJs with high ON/OFF ratios is a challenging task due to the vast search space comprising of ferroelectric and electrode materials,fabrication methods and conditions and so on.Here,machine learning(ML)is demonstrated to be an effective tool to guide the experimental search of FTJs with high ON/OFF ratios.A dataset consisting of 152 FTJ samples with nine features and one target attribute(i.e.,ON/OFF ratio)is established for ML modeling.Among various ML models,the gradient boosting classification model achieves the highest prediction accuracy.Combining the feature importance analysis based on this model with the association rule mining,it is extracted that the utilizations of{graphene/graphite(Gra)(top),LaNiO_(3)(LNO)(bottom)}and{Gra(top),Ca_(0.96)Ce_(0.04)MnO_(3)(CCMO)(bottom)}electrode pairs are likely to result in high ON/OFF ratios in FTJs.Moreover,two previously unexplored FTJs:Gra/BaTiO_(3)(BTO)/LNO and Gra/BTO/CCMO,are predicted to achieve ON/OFF ratios higher than 1000.Guided by the ML predictions,the Gra/BTO/LNO and Gra/BTO/CCMO FTJs are experimentally fabricated,which unsurprisingly exhibit≥1000 ON/OFF ratios(~8540 and~7890,respectively).This study demonstrates a new paradigm of developing high-performance FTJs by using ML.
基金Project supported by the National Natural Science Foundation of China(Grant No.61804055)"Chenguang Program"supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission,China(Grant No.17CG24)Shanghai Science and Technology Innovation Action Plan,China(Grant No.19JC1416700).
文摘The multiple ferroelectric polarization tuned by external electric field could be used to simulate the biological synaptic weight. Ferroelectric synaptic devices have two advantages compared with other reported ones: One is that the intrinsic switching of ferroelectric domains without invoking of defect migration as in resistive oxides, contributes reliable performance in these ferroelectric synapses. Another tremendous advantage is the extremely low energy consumption because the ferroelectric polarization is manipulated by electric field which eliminates the Joule heating by current as in magnetic and phase change memories. Ferroelectric synapses have potential for the construction of low-energy and effective brain-like intelligent networks. Here we summarize recent pioneering work of ferroelectric synapses involving the structure of ferroelectric tunnel junctions (FTJs), ferroelectric diodes (FDs), and ferroelectric field effect transistors (FeFETs), respectively, and shed light on future work needed to accelerate their application for efficient neural network.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11874244 and 11974222)。
文摘Modulation between optical and ferroelectric properties was realized in a lateral structured ferroelectric CuInP_(2)S_(6)(CIPS)/semiconductor MoS_(2) van der Waals heterojunction.The ferroelectric hysteresis loop area was modulated by the optical field.Two types of photodetection properties can be realized in a device by changing the ON and OFF states of the ferroelectric layer.The device was used as a photodetector in the OFF state but not in the ON state.The higher tunnelling electroresistance(~1.4×10^(4))in a lateral structured ferroelectric tunnelling junction was crucial,and it was analyzed and modulated by the barrier height and width of the ferroelectric CIPS/semiconductor MoS_(2) Schottky junction.The new parameter of the ferroelectric hysteresis loop area as a function of light intensity was introduced to analyze the relationship between the ferroelectric and photodetection properties.The proposed device has potential application as an optoelectronic sensory cell in the biological nervous system or as a new type of photodetector.
基金supported by the National Key Research and Development Program of China(2016YFA0300103 and 2019YFA0307900)National Natural Science Foundation of China(51790491,51972296 and 21521001)+1 种基金the Fundamental Research Funds for the Central Universities(WK2030000035)State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China。
文摘Ferroelectric tunnel junctions(FTJs)as the artificial synaptic devices have been considered promising for constructing brain-inspired neuromorphic computing systems.However,the memristive synapses based on the flexible FTJs have been rarely studied.Here,we report a flexible FTJ memristor grown on a mica substrate,which consists of an ultrathin ferroelectric barrier of BiFeO_(3),a semiconducting layer of ZnO,and an electrode of SrRuO_(3).The obtained flexible FTJ memristor exhibits stable voltage-tuned multistates,and the resistive switchings are robust after 10^(3) bending cycles.The capability of the FTJ as a flexible synaptic device is demonstrated by the functionality of the spike-timing-dependent plasticity with bending,and the accurate conductance manipulation with small nonlinearity(-0.24)and low cycle-to-cycle variation(1.77%)is also realized.Especially,artificial neural network simulations based on experimental device behaviors reveal that the high recognition accuracies up to 92.8%and 86.2%are obtained for handwritten digits and images,respectively,which are close to the performances for ideal memristors.This work highlights the potential applications of FTJ as flexible electronics for data storage and processing.
基金supported in part by National Natural Science Foundation(62274101,U20A20168,61874065,51861145202)of Chinain part by the National Key R&D Program(2021YFC3002200,2020YFA0709800,2018YFC2001202,2022Y FB3204100)of China+2 种基金in part by JCCDFSIT(2022CDF003)QYJS-2022-1600-BBNR2024RC01002.
文摘The emergence of data-centric applications such as artificial intelligence(AI),machine learning,and the Internet of Things(IoT),has promoted surges in demand for storage memories with high operating speed and nonvolatile characteristics.HfO_(2)-based ferroelectric memory technologies,which emerge as a promising alternative,have attracted considerable attention due to their high performance,energy efficiency,and full compatibility with the standard complementary metal-oxide-semiconductors(CMOS)process.These nonvolatile storage elements,such as ferroelectric random access memory(FeRAM),ferroelectric field-effect transistors(FeFETs),and ferroelectric tunnel junctions(FTJs),possess different data access mechanisms,individual merits,and specific application boundaries in next-generation memories or even beyond von Neumann architecture.This paper provides an overview of ferroelectric HfO2 memory technologies,addresses the current challenges,and offers insights into future research directions and prospects.
基金supported by grants from the National Natural Science Foundation of China(Nos.52272172,61888102,and 52102193)the Major Program of National Natural Science Foundation of China(No.92163206)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB30000000)the Fundamental Research Funds for the Central Universities.Computational resources were provided by the National Supercomputing Center in Tianjin.
文摘Two-dimensional(2D)ferroelectric(FE)materials with relatively low switching barrier and large polarization are promising candidates for next-generation miniaturized nonvolatile memory devices.Herein,we screen out 39 new 2D ferroelectric materials,MX(M:Group III-V elements;X:Group V-VII elements),in three phosphorus-analogue phases including black phosphorene-likeα-phase,blue phosphorus-likeβ-phase,and GeSe-likeγ-phase using high-throughput calculations.Seven materials(α-SbP,γ-AsP,etc.)exhibit FE switching barriers lower than 0.3 eV/f.u.,ferroelectric polarization larger than 2×10^(−10)C/m,and high thermodynamic stability with energy above hull smaller than 0.2 eV/atom.We find that the larger the electronegativity difference between M and X,the larger the ferroelectric polarization.Moreover,larger electronegativity differences result in lower in-plane piezoelectric stress tensor(e11)for MX consisting of Group IV and VI elements and larger e11 for those consisting of Group V elements.Further calculations predict a giant tunneling electroresistance in ferroelectric tunnel junctionα-Sb(Sn)P/α-SbP/α-Sb(Te)P(1.26×104%)and large piezoelectric strain coefficient inα-SnTe(396 pm/V),providing great opportunities to the design of non-volatile resistive memories,and high-performance piezoelectric devices.
