Hafnium zirconium oxides(HZO),which exhibit ferroelectric properties,are promising materials for nanoscale device fabrication due to their high complementary metal-oxide-semiconductor(CMOS) compatibility.In addition t...Hafnium zirconium oxides(HZO),which exhibit ferroelectric properties,are promising materials for nanoscale device fabrication due to their high complementary metal-oxide-semiconductor(CMOS) compatibility.In addition to piezoelectricity,ferroelectricity,and flexoelectricity,this study reports the observation of ferroelasticity using piezoelectric force microscopy(PFM) and scanning transmission electron microscopy(STEM).The dynamics of 90° ferroelastic domains in HZO thin films are investigated under the influence of an electric field.Switching of the retentive domains is observed through repeated wake-up measurements.This study presents a possibility of enhancing polarization in HZO thin films during wake-up processes.展开更多
Magnetoelectric composites and heterostructures integrate magnetic and dielectric materials to produce new functionalities,e.g.,magnetoelectric responses that are absent in each of the constituent materials but emerge...Magnetoelectric composites and heterostructures integrate magnetic and dielectric materials to produce new functionalities,e.g.,magnetoelectric responses that are absent in each of the constituent materials but emerge through the coupling between magnetic order in the magnetic material and electric order in the dielectric material.The magnetoelectric coupling in these composites and heterostructures is typically achieved through the exchange of magnetic,electric,or/and elastic energy across the interfaces between the different constituent materials,and the coupling effect is measured by the degree of conversion between magnetic and electric energy in the absence of an electric current.The strength of magnetoelectric coupling can be tailored by choosing suited materials for each constituent and by geometrical and microstructural designs.In this article,we discuss recent progresses on the understanding of magnetoelectric coupling mechanisms and the design of magnetoelectric heterostructures guided by theory and computation.We outline a number of unsolved issues concerning magnetoelectric heterostructures.We compile a relatively comprehensive experimental dataset on the magnetoelecric coupling coefficients in both bulk and thin-film magnetoelectric composites and offer a perspective on the data-driven computational design of magnetoelectric composites at the mesoscale microstructure level.展开更多
Valley,the energy extrema in the electronic band structure at momentum space,is regarded as a new degree of freedom of electrons,in addition to charge and spin.The studies focused on valley degree of freedom now form ...Valley,the energy extrema in the electronic band structure at momentum space,is regarded as a new degree of freedom of electrons,in addition to charge and spin.The studies focused on valley degree of freedom now form an emerging field of condensed-matter physics,i.e.,valleytronics,whose development is exactly following that of spintronics,which focuses on the spin degree of freedom.展开更多
Based on density-functional calculations,we have studied possible ferroelectric switching path in monodomain single crystal of rhombohedral BiFeO_(3),a prototypical multiferroic compound.By carefully studying the beha...Based on density-functional calculations,we have studied possible ferroelectric switching path in monodomain single crystal of rhombohedral BiFeO_(3),a prototypical multiferroic compound.By carefully studying the behaviors of FeO_(3)corner-sharing double-tetrahedrons,we find abrupt changes in total energy and oxygen atomic positions,and therefore polarizations,occur in the ferroelectric switching path of rhombohedral BiFeO_(3).Detailed analyses suggest that such behavior might be caused by the frustrated magnetic ordering in the paraelectric phase of rhombohedral BiFeO_(3),where three O atoms and the Bi atom are in the same plane perpendicular to the polar-ization direction.This is supported by the fact that the ferroelectric switching for paramagnetic BiFeO_(3)is smooth and has a much lower energy barrier than that of an tiferromagnetic BiFeO_(3).展开更多
Owing to the outstanding properties provided by nontrivial band topology,topological phases of matter are considered as a promising platform towards low-dissipation electronics,efficient spin-charge conversion,and top...Owing to the outstanding properties provided by nontrivial band topology,topological phases of matter are considered as a promising platform towards low-dissipation electronics,efficient spin-charge conversion,and topological quantum computation.Achieving ferroelectricity in topological materials enables the non-volatile control of the quantum states,which could greatly facilitate topological electronic research.However,ferroelectricity is generally incompatible with systems featuring metallicity due to the screening effect of free carriers.In this study,we report the observation of memristive switching based on the ferroelectric surface state of a topological semimetal(TaSe_(4))2I.We find that the surface state of(TaSe_(4))2I presents out-of-plane ferroelectric polarization due to surface reconstruction.With the combination of ferroelectric surface and charge-density-wave-gapped bulk states,an electric-switchable barrier height can be achieved in(TaSe_(4))2I-metal contact.By employing a multi-terminal-grounding design,we manage to construct a prototype ferroelectric memristor based on(TaSe_(4))2I with on/off ratio up to 103,endurance over 103 cycles,and good retention characteristics.The origin of the ferroelectric surface state is further investigated by first-principles calculations,which reveal an interplay between ferroelectricity and band topology.The emergence of ferroelectricity in(TaSe_(4))2I not only demonstrates it as a rare but essential case of ferroelectric topological materials,but also opens new routes towards the implementation of topological materials in functional electronic devices.展开更多
基金Project supported by the the National Key Research and Development Program of China (Grant No. 2022YFA1402902)the National Natural Science Foundation of China (Grant Nos. 12074119, 12204171, 12134003, and 12374145)+1 种基金the Chenguang Program Foundation of Shanghai Education Development Foundation and Shanghai Municipal Education Commission, ECNU (East China Normal University) Multifunctional Platform for Innovation (006)the Fundamental Research Funds for the Central Universities。
文摘Hafnium zirconium oxides(HZO),which exhibit ferroelectric properties,are promising materials for nanoscale device fabrication due to their high complementary metal-oxide-semiconductor(CMOS) compatibility.In addition to piezoelectricity,ferroelectricity,and flexoelectricity,this study reports the observation of ferroelasticity using piezoelectric force microscopy(PFM) and scanning transmission electron microscopy(STEM).The dynamics of 90° ferroelastic domains in HZO thin films are investigated under the influence of an electric field.Switching of the retentive domains is observed through repeated wake-up measurements.This study presents a possibility of enhancing polarization in HZO thin films during wake-up processes.
基金financial support from National Science Foundation(NSF)under Grant DMR-1235092 and DMR-1410714financial support from the National Key Project for Basic Research of China(Grant Nos.2014CB921104)+2 种基金the NSF of China(Grant No.51572085)supported by the NSF of China(Grant Nos.51332001 and 51472140)Tsinghua University with Grant No.2014z01006.
文摘Magnetoelectric composites and heterostructures integrate magnetic and dielectric materials to produce new functionalities,e.g.,magnetoelectric responses that are absent in each of the constituent materials but emerge through the coupling between magnetic order in the magnetic material and electric order in the dielectric material.The magnetoelectric coupling in these composites and heterostructures is typically achieved through the exchange of magnetic,electric,or/and elastic energy across the interfaces between the different constituent materials,and the coupling effect is measured by the degree of conversion between magnetic and electric energy in the absence of an electric current.The strength of magnetoelectric coupling can be tailored by choosing suited materials for each constituent and by geometrical and microstructural designs.In this article,we discuss recent progresses on the understanding of magnetoelectric coupling mechanisms and the design of magnetoelectric heterostructures guided by theory and computation.We outline a number of unsolved issues concerning magnetoelectric heterostructures.We compile a relatively comprehensive experimental dataset on the magnetoelecric coupling coefficients in both bulk and thin-film magnetoelectric composites and offer a perspective on the data-driven computational design of magnetoelectric composites at the mesoscale microstructure level.
基金This work was supported by the National Key Research and Development Program of China(2017YFA0303403)Shanghai Science and Technology Innovation Action Plan(No.19JC1416700)+1 种基金the NSF of China(No.51572085,11774092)ECNU Multifunctional Platform for Innovation.
文摘Valley,the energy extrema in the electronic band structure at momentum space,is regarded as a new degree of freedom of electrons,in addition to charge and spin.The studies focused on valley degree of freedom now form an emerging field of condensed-matter physics,i.e.,valleytronics,whose development is exactly following that of spintronics,which focuses on the spin degree of freedom.
基金the NSF of China(Grant No.50771072 and 50832003)PCSIRT,Shanghai Pujiang and ShuGuang Program,and 973 Program No.2007CB924900.
文摘Based on density-functional calculations,we have studied possible ferroelectric switching path in monodomain single crystal of rhombohedral BiFeO_(3),a prototypical multiferroic compound.By carefully studying the behaviors of FeO_(3)corner-sharing double-tetrahedrons,we find abrupt changes in total energy and oxygen atomic positions,and therefore polarizations,occur in the ferroelectric switching path of rhombohedral BiFeO_(3).Detailed analyses suggest that such behavior might be caused by the frustrated magnetic ordering in the paraelectric phase of rhombohedral BiFeO_(3),where three O atoms and the Bi atom are in the same plane perpendicular to the polar-ization direction.This is supported by the fact that the ferroelectric switching for paramagnetic BiFeO_(3)is smooth and has a much lower energy barrier than that of an tiferromagnetic BiFeO_(3).
基金supported by the National Key R&D Program of China(2022YFA1405700)the National Natural Science Foundation of China(12174069 and 92365104)+8 种基金Shuguang Program from the Shanghai Education Development Foundationsupported by the National Key R&D Program of China(2023YFA1407500)the National Natural Science Foundation of China(12174104 and 62005079)supported by the National Key R&D Program of China(2022YFA1402901)National Natural Science Foundation of China(12274082)Shanghai Science and Technology Committee(23ZR1406600)Shanghai Pilot Program for Basic Research-FuDan University 21TQ1400100(23TQ017)supported by the China Postdoctoral Science Foundation(2022M720816)supported by the National Key R&D Program of China(2022YFA1402902)。
文摘Owing to the outstanding properties provided by nontrivial band topology,topological phases of matter are considered as a promising platform towards low-dissipation electronics,efficient spin-charge conversion,and topological quantum computation.Achieving ferroelectricity in topological materials enables the non-volatile control of the quantum states,which could greatly facilitate topological electronic research.However,ferroelectricity is generally incompatible with systems featuring metallicity due to the screening effect of free carriers.In this study,we report the observation of memristive switching based on the ferroelectric surface state of a topological semimetal(TaSe_(4))2I.We find that the surface state of(TaSe_(4))2I presents out-of-plane ferroelectric polarization due to surface reconstruction.With the combination of ferroelectric surface and charge-density-wave-gapped bulk states,an electric-switchable barrier height can be achieved in(TaSe_(4))2I-metal contact.By employing a multi-terminal-grounding design,we manage to construct a prototype ferroelectric memristor based on(TaSe_(4))2I with on/off ratio up to 103,endurance over 103 cycles,and good retention characteristics.The origin of the ferroelectric surface state is further investigated by first-principles calculations,which reveal an interplay between ferroelectricity and band topology.The emergence of ferroelectricity in(TaSe_(4))2I not only demonstrates it as a rare but essential case of ferroelectric topological materials,but also opens new routes towards the implementation of topological materials in functional electronic devices.