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Designing two-dimensional ferroelectric materials from phosphorus-analogue structures

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Nano Research 2023年第4期16卷 5834-5842页

作者： Ziyuan Liu Lei Tao yan-fang zhang Jinbo Pan Shixuan Du Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Chinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China CAS Center for Excellence in Topological Quantum Computation Beijing 100190China

Two-dimensional(2D)ferroelectric(FE)materials with relatively low switching barrier and large polarization are promising candidates for next-generation miniaturized nonvolatile memory ***,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 *** 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/*** find that the larger the electronegativity difference between M and X,the larger the ferroelectric ***,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 *** 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.

关键词： two-dimensional(2D)materials ferroelectricity piezoelectricity ferroelectric tunnel junction

Two-dimensional MX Dirac materials and quantum spin Hall insulators with tunable electronic and topological properties

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Nano Research 2021年第3期14卷 584-589页

作者： yan-fang zhang Jinbo Pan Huta Banjade Jie Yu Hsin Lin Arun Bansil Shixuan Du Qimin yan Institute of Physics&University of Chinese Academy of Sciences Chinese Academy of SciencesBeijing100190China Department of Physics Temple UniversityPhiladelphiaPA19122USA Institute of Physics “Academia Sinica”Taipei11529Taiwan Physics Department Northeastern UniversityBostonMA02115USA

We propose a novel class of two-dimensional(2D)Dirac materials in the MX family(M=Be,Mg,Zn and Cd,X=Cl,Br and I),which exhibit graphene-like band structures with linearly-dispersing Dirac-cone states over large energy scales(0.8–1.8 eV)and ultra-high Fermi velocities comparable to ***-orbit coupling opens sizable topological band gaps so that these compounds can be effectively classified as quantum spin Hall *** electronic and topological properties are found to be highly tunable and amenable to modulation via anion-layer substitution and vertical electric *** structures of several members of the family are shown to host a Van-Hove singularity(VHS)close to the energy of the Dirac *** enhanced density-of-states associated with these VHSs could provide a mechanism for inducing topological *** presence of sizable band gaps,ultra-high carrier mobilities,and small effective masses makes the MX family promising for electronics and spintronics applications.

关键词： two-dimensional Dirac materials density functional theory topological properties

Ultra-low Young’s modulus and high super-exchange interactions in monolayer CrN: A promising candidate for flexible spintronic applications

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Chinese Physics B 2021年第4期30卷 459-464页

作者： yang Song yan-fang zhang Jinbo Pan Shixuan Du Institute of Physics and School of Physical Sciences University of Chinese Academy of SciencesChinese Academy of SciencesBeijing 100190China

Monolayer CrN has been predicted to be half-metallic ferromagnet with high Curie *** to bulk CrN’s biocompatibility,the monolayer is a promising candidate for bio-related ***,using first-principles calculations based on density functional theory,we find that the formation energy of the bulk CrN stacking from layers with square lattice is only 68 meV/atom above the convex hull,suggesting a great potential to fabricate the monolayer CrN in a square lattice by using molecular beam epitaxy *** monolayer CrN is then proved to be a soft material with an ultra-low Young’s modulus and can sustain very large ***,the analysis of the projected density of states demonstrates that the ferromagnetic half-metallicity originates from the splitting of Cr-d orbitals in the CrN square crystal field,the bonding interaction between Cr-N,and that between Cr-Cr *** is worth noting that the super-exchange interaction is much larger than the direct-exchange interaction and contributes to the ultra-high Curie temperature,which is obtained from Monte Carlo simulations based on Heisenberg *** findings suggest that the monolayer CrN can be an indispensable candidate for nanoscale flexible spintronic applications with good biocompatibility and is considerable appealing to be realized in experiment.

关键词： monolayer Cr N half-metallic ferromagnet flexible material spintronics

Effects of BN content on the mechanical properties of nanocrystalline 3Y-TZP/Al_(2)O_(3)/BN dental ceramics

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International Journal of Minerals,Metallurgy and Materials 2021年第11期28卷 1854-1860页

作者： Lei Zhou yan-fang zhang Pan Yi Ying Wen Chao-fang Dong Li-min Meng Se-fei yang Medical School of Chinese PLA Beijing 100853China Department of Stomatology The First Medical CenterChinese PLA General HospitalBeijing 100853China Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China Journals Publishing Center University of Science and Technology BeijingBeijing 100083China Department of Medical Imaging Air Force Medical CenterPLABeijing 100142China

3Y-TZP/3wt%Al_(2)O_(3) powder was coated with varying amounts of BN using the urea and borate reaction sintering method,and then multiphase ceramics were prepared by hot pressing *** micro-topography and the compositional analysis of synthesized ceramics were conducted through scanning electron microscopy,transmission electron microscopy and X-ray diffraction.A mechanical tester was used to analyze the Vickers hardness,fracture toughness,and bending strength of the synthesized *** results showed that the ceramic with a BN content of 12wt%showed the best processability,but had diminished mechanical properties(such as fracture toughness and bending strength).The ceramic with a BN content of 9wt%showed better processability than those with 3wt%and 6wt%***,the fracture toughness was affected by the addition of 9wt%BN,making this ceramic only usable as a base material for a three-unit fixed *** contrast,the ceramics with a BN content of 3wt%or 6wt%fulfilled the criteria for use in multi-unit restoration,but their low processability made them unsuitable for milling after sintering.

关键词： multiphase ceramic boron nitride mechanical properties reaction sintering method

Superconductivity and topological aspects of two-dimensional transition-metal monohalides

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npj Computational Materials 2022年第1期8卷 1763-1770页

作者： Wen-Han Dong Yu-yang zhang yan-fang zhang Jia-Tao Sun Feng Liu Shixuan Du Beijing National Center for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing100049China CAS Center for Excellence in Topological Quantum Computation Beijing100190China School of Integrated Circuits and Electronics MIIT Key Laboratory for Low-Dimensional Quantum Structure and DevicesBeijing Institute of TechnologyBeijing100081China Department of Materials Science and Engineering University of UtahSalt Lake CityUtah84112USA Songshan Lake Materials Laboratory Dongguan523808China

Two-dimensional(2D)superconducting states have attracted much recent interest,especially when they coexist with nontrivial band topology which affords a promising approach towards Majorana *** first-principles calculations,we predict van der Waals monolayered transition-metal monohalides MX(M=Zr,Mo;X=F,Cl)as a class of 2D superconductors with remarkable transition temperature(5.9–12.4 K).Anisotropic Migdal-Eliashberg theory reveals that ZrCl have a single superconducting gap∆~2.14 meV,while MoCl is a two-gap superconductor with∆~1.96 and 1.37 *** Z_(2)band topology of 2D MX is further demonstrated that MoF and MoCl are candidates for realizing topological ***,the Dirac phonons of ZrCl and MoCl contribute w-shape phononic edge states,which are potential for an edge-enhanced electron-phonon *** findings demonstrate that 2D MX offers an attractive platform for exploring the interplay between superconductivity,nontrivial electronic and phononic topology.

关键词： topological transition nontrivial

Band engineering of honeycomb monolayer CuSe via atomic modification

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Chinese Physics B 2021年第10期30卷 495-499页

作者： Lei Gao yan-fang zhang Jia-Tao Sun Shixuan Du Faculty of Science Kunming University of Science and TechnologyKunming 650000China Institute of Physics and University of Chinese Academy of SciencesChinese Academy of SciencesBeijing 100190China School of Information and Electronics Beijing Institute of TechnologyBeijing 100081China

Two-dimensional monolayer copper selenide(CuSe)has been epitaxially grown and predicted to host the Dirac nodal line fermion(DNLF).However,the metallic state of monolayer CuSe inhibits the potential application of nanoelectronic devices in which a band gap is needed to realize on/off ***,we engineer the band structure of monolayer CuSe which is an analogue of a p-doped system via external atomic modification in an effort to realize the semiconducting *** find that the H and Li modified monolayer CuSe shifts the energy band and opens an energy gap around the Fermi ***,both the atomic and electronic structures of monolayer CuHSe and CuLiSe are very *** H atoms bind on top of Se atoms of monolayer CuSe with Se-H polar covalent bonds,annihilating the DNLF band of monolayer CuSe dominated by Se *** contrast,Li atoms prefer to adsorb at the hexagonal center of CuSe,preserving the DNLF band of monolayer CuSe dominated by Se orbitals,but opening band gaps due to a slight buckling of the CuSe *** realization of metal-to-semiconductor transition from monolayer CuSe to CuXSe(X=H,Li)as revealed by first-principles calculations makes it possible to use CuSe in future electronic devices.

关键词： first-principles calculations monolayer CuSe band engineering

Quantum anomalous Hall effect in two-dimensional magnetic insulator heterojunctions

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npj Computational Materials 2020年第1期6卷 405-412页

作者： Jinbo Pan Jiabin Yu yan-fang zhang Shixuan Du Anderson Janotti Chao-Xing Liu Qimin yan Department of Physics Temple UniversityPhiladelphiaPA 19122USA Department of Physics The Pennsylvania State UniversityUniversity ParkPA 16802USA Condensed Matter Theory Center Department of PhysicsUniversity of MarylandCollege ParkMaryland 20742USA Institute of Physics Chinese Academy of ScienceBeijing 100190China Department of Materials Science and Engineering University of DelawareDE 19716 WilmingtonUSA

Recent years have witnessed tremendous success in the discovery of topological states of ***,sophisticated theoretical methods in time-reversal-invariant topological phases have been developed,leading to the comprehensive search of crystal database and the prediction of thousands of topological *** contrast,the discovery of magnetic topological phases that break time reversal is still limited to several exemplary materials because the coexistence of magnetism and topological electronic band structure is rare in a single *** overcome this challenge,we propose an alternative approach to realize the quantum anomalous Hall(QAH)effect,a typical example of magnetic topological phase,via engineering two-dimensional(2D)magnetic van der Waals heterojunctions.

关键词： magnetic anomalous effect

Transition of photoconductive and photovoltaic operation modes in amorphous Ga_2O_3-based solar-blind detectors tuned by oxygen vacancies

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Chinese Physics B 2019年第2期28卷 71-76页

作者： yan-fang zhang Xuan-Hu Chen yang Xu fang-fang Ren Shu-Lin Gu Rong zhang You-Dou Zheng Jian-Dong Ye Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials and School of Electronic Science and Engineering Nanjing University Wuxi Institute of Technology Collaborative Innovation Center of Solid-State Lighting and Energy-Saving Electronics Nanjing University

We report on the transition of photovoltaic and photoconductive operation modes of the amorphous Ga_2O_3-based solar-blind photodetectors in metal–semiconductor–metal(MSM) configurations. The conversion from Ohmic to Schottky contacts at Ti/Ga_2O_3 interface is realized by tuning the conductivity of amorphous Ga_2O_3 films with delicate control of oxygen flux in the sputtering process. The abundant donor-like oxygen vacancies distributed near the Ti/Ga_2O_3 interface fascinate the tunneling process across the barrier and result in the formation of Ohmic contacts. As a consequence, the serious sub-gap absorption and persistent photoconductivity(PPC) effect degrades the performance of the photoconductive detectors. In contrast, the photovoltaic device with a Schottky contact exhibits an ultra-low dark current less than 1 pA,a high detectivity of 9.82×10^(12) cm·Hz^(1/2)·W^(-1), a fast response time of 243.9 μs, and a high ultraviolet C(UVC)-toultraviolet A(UVA) rejection ratio of 103. The promoting performance is attributed primarily to the reduction of the subgap states and the resultant suppression of PPC effect. With simple architecture, low fabrication cost, and easy fusion with modern high-speed integrated circuitry, these results provide a cost-effective way to realize high performance solar-blind photodetectors towards versatile practical applications.

关键词： amorphous gallium oxide solar-blind photodetector photovoltaic photoconductive

Auxetic two-dimensional transition metal selenides and halides

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npj Computational Materials 2020年第1期6卷 387-392页

作者： Jinbo Pan yan-fang zhang Jingda zhang Huta Banjade Jie Yu Liping Yu Shixuan Du Adrienn Ruzsinszky Zhenpeng Hu Qimin yan Department of Physics Temple UniversityPhiladelphiaPA 19122USA Institute of Physics Chinese Academy of SciencesBeijing 100190China School of Physics Nankai UniversityTianjin 300071China Department of Physics and Astronomy University of MaineOronoME 04469USA

Auxetic two-dimensional(2D)materials provide a promising platform for biomedicine,sensors,and many other applications at the *** this work,utilizing a hypothesis-based data-driven approache,we identify multiple materials with remarkable in-plane auxetic behavior in a family of buckled monolayer 2D *** materials are transition metal selenides and transition metal halides with the stoichiometry MX(M=V,Cr,Mn,Fe,Co,Cu,Zn,Ag,and X=Se,Cl,Br,I).First-principles calculations reveal that the desirable auxetic behavior of these 2D compounds originates from the interplay between the buckled 2D structure and the weak metal-metal interaction determined by their electronic *** observe that the Poisson’s ratio is sensitive to magnetic order and the amount of uniaxial stress applied.A transition from positive Poisson’s ratio(PPR)to negative Poisson’s ratio(NPR)for a subgroup of MX compounds under large uniaxial stress is *** work provides a guideline for the future design of 2D auxetic materials at the nanoscale.

关键词： materials transition dimensional