Battery materials as emerging capacitive deionization electrodes for desalination have better salt removal capacities than traditional carbon-based materials.LiMn_(2)O_(4),a widely used cathode mate-rial,is difficult ...Battery materials as emerging capacitive deionization electrodes for desalination have better salt removal capacities than traditional carbon-based materials.LiMn_(2)O_(4),a widely used cathode mate-rial,is difficult to utilize as a deionization electrode due to its structural instability upon cycling and Mn dissolution in aqueous-based electrolytes.Herein,a facile and low-cost ball-milling routine was proposed to prepare a LiMn_(2)O_(4)material with highly exposed(111)facets.The prepared electrode exhibited relatively low dissolution of Mn during cycling,which shows its long cycle stability.In the hybrid capacitive deionization system,the LiMn_(2)O_(4)/C electrode delivered a high desalination capacity of 117.3 mg g^(−1) without obvious capacity decay at a voltage of 1.0 V with a 20 mM initial salt concentration.In addition,the exposed(111)facets significantly alleviated Mn ion dissolution,which also enhanced the structural steadiness.展开更多
Hybrid organic–inorganic perovskite thin films have attracted much attention in optoelectronic and information fields because of their intriguing properties. Due to quantum confinement effects, ultrathin films in nm ...Hybrid organic–inorganic perovskite thin films have attracted much attention in optoelectronic and information fields because of their intriguing properties. Due to quantum confinement effects, ultrathin films in nm scale usually show special properties. Here, we report on the growth of methylammonium lead iodide(MAPbI_(3)) ultrathin films via co-deposition of PbI_2 and CH_3NH_3I(MAI) on chemical-vapor-deposition-grown monolayer MoS_(2) as well as the corresponding photoluminescence(PL) properties at different growing stages. Atomic force microscopy and scanning electron microscopy measurements reveal the MoS_(2) tuned growth of MAPbI_(3) in a Stranski–Krastanov mode. PL and Kelvin probe force microscopy results confirm that MAPbI_(3) /MoS_(2) heterostructures have a type-Ⅱ energy level alignment at the interface. Temperaturedependent PL measurements on layered MAPbI_(3) (at the initial stage) and on MAPbI_(3) crystals in averaged size of 500 nm(at the later stage) show rather different temperature dependence as well as the phase transitions from tetragonal to orthorhombic at 120 and 150 K, respectively. Our findings are useful in fabricating MAPbI_(3) /transition-metal dichalcogenide based innovative devices for wider optoelectronic applications.展开更多
Stacking-dependent magnetism in van der Waals materials has caught intense interests.Based on the first principle calculations,we investigate the coupling between stacking orders and interlayer magnetic orders in bila...Stacking-dependent magnetism in van der Waals materials has caught intense interests.Based on the first principle calculations,we investigate the coupling between stacking orders and interlayer magnetic orders in bilayer H-VSe 2.It is found that there are two stable stacking orders in bilayer H-VSe 2,named AB-stacking and A′B-stacking.Under standard DFT framework,the A′B-stacking prefers the interlayer AFM order and is semiconductive,whereas the AB-stacking prefers the FM order and is metallic.However,under the DFT+U framework both the stacking orders prefer the interlayer AFM order and are semiconductive.By detailedly analyzing this difference,we find that the interlayer magnetism originates from the competition between antiferromagnetic interlayer super-superexchange and ferromagnetic interlayer double exchange,in which both the interlayer Se-4 p z orbitals play a crucial role.In the DFT+U calculations,the double exchange is suppressed due to the opened bandgap,such that the interlayer magnetic orders are decoupled with the stacking orders.Based on this competition mechanism,we propose that a moderate hole doping can significantly enhance the interlayer double exchange,and can be used to switch the interlayer magnetic orders in bilayer VSe 2.This method is also applicable to a wide range of semiconductive van der Waals magnets.展开更多
Developing an effective catalyst for the selective oxidation of hydrocarbon to high value-added compounds remains as a challenge in terms of the growing global concerns about green chemistry and environmental sustaina...Developing an effective catalyst for the selective oxidation of hydrocarbon to high value-added compounds remains as a challenge in terms of the growing global concerns about green chemistry and environmental sustainability.Herein,asymmetric nitrogen and phosphorus co-coordinated Ce single-atom sites(Ce-N_(3)P-C)were constructed for the activation of aromatic C-H bond.Ce-N_(3)P-C demonstrates excellent catalytic performance for efficient solvent-free aerobic oxidation of aromatic C-H bonds,especially for oxidation of ethylbenzene with 97%selectivity of acetophenone and high stability.The turnover frequency(TOF)value is 536 h-1,which is the highest level among reported non-precious-metal catalysts in a similar system.The partial substitution of coordinated N with P atom breaks the symmetry of the active moiety of Ce and raises the electron density of Ce center.The reduced valence state of metallic Ce indicates that more electrons could transfer to the antibonding π-orbital of the adsorbed O_(2),thus promoting the subsequent free radical reaction and accelerating the rate-determining step.The breaking of coordination symmetry of single-atom site catalyst by introducing heteroatoms to tune its active moiety paves a way to boost the catalytic performance of similar catalysts.展开更多
Atomically thin two-dimensional(2D)magnetic materials offer unique opportunities to enhance interactions between electron spin,charge,and lattice,leading to novel physical properties at low-dimensional scales.While ex...Atomically thin two-dimensional(2D)magnetic materials offer unique opportunities to enhance interactions between electron spin,charge,and lattice,leading to novel physical properties at low-dimensional scales.While extensive research has explored how breaking three-fold(Cs)rotational symmetry in transition metal dichalcogenides(TMDC)can induce optical anisotropy at heterointerfaces,the role of magnetism in modulating these anisotropic optical properties remainsunderexplored.anHere,engineerwe antiferromagnet/semiconductor heterostructure by coupling isotropic MoWSe_(2) with the low-symmetric antiferromagnet NiPSs,introducing in-plane anisotropy in the MoWSe_(2) alloy.Low-temperature photoluminescence(PL)measurements reveal a pronounced linear polarization-dependent exciton emission intensity at the MoWSe_(2)/NiPS interface,with anisotropy ratios of 1.09 and 1.07 for charged and neutral excitons,respectively.Furthermore,applying an out-of-plane magnetic field results in a dramatic rotation of the exciton polarization direction by up to 90°at 9 T,significantly exceeding the previously reported maximum deflection of around 27°.This pronounced polarization rotation is not solely attributed to valley coherence,indicating a strong influence of the magnetic order in NiPS3.These findings provide new insights into the role of magnetic ordering in tuning optical anisotropy in 2D materials,paving the way for the development of advanced polarization-sensitive optoelectronic and magneto-optic devices.展开更多
The ferrovalley materials and their nontrivial band topological properties have recently attracted extensive interest in theoretical physics and their promising applications.Using first-principles calculations,we pred...The ferrovalley materials and their nontrivial band topological properties have recently attracted extensive interest in theoretical physics and their promising applications.Using first-principles calculations,we predict the valley polarization in monolayer Mo_(S)nC_(2)S_(6) and MoPbGe_(2)Te_(6).These materials possess a robust ferromagnetic ground state,with high Curie temperatures of 460 K and 319.5 K,respectively.The intrinsic valley polarization arises from the breaking of time-reversal symmetry and spatial inversion symmetry.Biaxial strain and electron correlation(U)can modulate the valley polarization and bandgap.The quantum anomalous Hall phase is driven by biaxial strain and U during the process of bandgap closing,opening,reclosing,and reopening.This can be demonstrated by the chiral edge states at the edges and the plateau in the anomalous Hall conductivity.During the closing and opening of the bandgap,the sign and magnitude of the Berry curvature also vary.Our work provides an ideal platform for valleytronics and the quantum anomalous Hall effect.展开更多
Elementary excitations,such as in-plane anisotropic phonons and phonon polaritons(PhPs),inα-MoO_(3) play key roles in its outstanding physical properties like high carrier mobility and ultralow phonon thermal conduct...Elementary excitations,such as in-plane anisotropic phonons and phonon polaritons(PhPs),inα-MoO_(3) play key roles in its outstanding physical properties like high carrier mobility and ultralow phonon thermal conductivity().Understanding the excitation mechanisms like phonon–phonon interactions is the most fundamental step to further applications.Here,we report on the systematic Raman investigations on phonon anisotropy and anharmonicity of representative Mo–O stretching vibration phonon modes(SVPMs)in physical vapor deposition(PVD)-grownα-MoO_(3) flakes.Polarizations of SVPMs verify the phonon anisotropy.The abnormal temperature dependence of SVPMs reveals that giant quartic-phonon decay dominates the phonon anharmonicity inα-MoO_(3).An ultrashort phonon lifetime of~0.34 ps gives evidence of theoretically predicted ultralow inα-MoO_(3).Our findings give deep insight into the phonon–phonon interactions inα-MoO_(3) and provide an indicator for its extreme thermal device applications.展开更多
Moiré superlattices based on twisted transition metal dichalcogenide (TMD) heterostructures have recently emerged as a promising platform for probing novel and distinctive electronic phenomena in two-dimensional ...Moiré superlattices based on twisted transition metal dichalcogenide (TMD) heterostructures have recently emerged as a promising platform for probing novel and distinctive electronic phenomena in two-dimensional (2D) materials. By stacking TMD monolayers with a small twist angle, these superlattices create a periodic modulation of the electronic density of states, leading to the formation of mini bands. These mini bands can exhibit intriguing properties such as flat bands, correlated electron behavior, and unconventional superconductivity. This review provides a comprehensive overview of recent progress in Moiré superlattices formed from twisted TMD heterostructures. It covers the theoretical principles and experimental techniques for creating and studying these superlattices, and explores their potential applications in optoelectronics, quantum computing, and energy harvesting. The review also addresses key challenges, such as improving the scalability and reproducibility of the fabrication process, emphasizing the exciting opportunities and ongoing hurdles in this rapidly evolving field.展开更多
Two-dimensional transition metal dichalcogenides(TMDs)exhibit promising application prospects in the domains of electronic devices,optoelectronic devices and spintronic devices due to their distinctive energy band str...Two-dimensional transition metal dichalcogenides(TMDs)exhibit promising application prospects in the domains of electronic devices,optoelectronic devices and spintronic devices due to their distinctive energy band structures and spin−orbit coupling properties.Cr-based chalcogenides with narrow or even zero bandgap,covering from semiconductors to metallic materials,have considerable potential for wide-band photodetection and two-dimensional magnetism.Currently,the preparation of 2D CrX_(n)(X=S,Se,Te)nanosheets primarily relies on chemical vapor deposition(CVD)and molecule beam epitaxy(MBE),which enable the production of high-quality large-area materials.This review article focuses on recent progress of 2D Cr-based chalcogenides,including unique crystal structure of the CrX_(n)system,phase-controlled synthesis,and heterojunction construction.Furthermore,a detailed introduction of room-temperature ferromagnetism and electrical/optoelectronic properties of 2D CrXn is presented.Ultimately,this paper summarizes the challenges associated with utilizing 2D Cr-based chalcogenides in preparation strategies,optoelectronics devices,and spintronic devices while providing further insights.展开更多
Pressure exerts a profound influence on atomic configurations and interlayer interactions, thereby modulating the electronic and structural properties of materials. While high pressure has been observed to induce a st...Pressure exerts a profound influence on atomic configurations and interlayer interactions, thereby modulating the electronic and structural properties of materials. While high pressure has been observed to induce a structural phase transition in bulk PdSe_(2) crystals, leading to a transition from semiconductor to metal, the high-pressure behavior of few-layer PdSe_(2) remains elusive. Here, employing diamond anvil cell (DAC) techniques and high-pressure Raman spectroscopy, we investigate the structural evolution of layer-dependent PdSe_(2) under high pressure. We reveal that pressure significantly enhances interlayer coupling in PdSe_(2), driving structural phase transitions from an orthorhombic to a cubic phase. We demonstrate that PdSe_(2) crystals exhibit distinct layer-dependent pressure thresholds during the phase transition, with the decrease of transition pressure as the thickness of PdSe_(2) increases. Furthermore, our results of polarized Raman spectra confirm a reduction in material anisotropy with increasing pressure. This study offers crucial insights into the structural evolution of layer-dependent van der Waals materials under pressure, advancing our understanding of their pressure-induced behaviors.展开更多
Two-dimensional hafnium-based semiconductors and their heterostructures with native oxides have been shown unique physical properties and potential electronic and optoelectronic applications.However,the scalable synth...Two-dimensional hafnium-based semiconductors and their heterostructures with native oxides have been shown unique physical properties and potential electronic and optoelectronic applications.However,the scalable synthesis methods for ultrathin layered hafnium-based semiconductor laterally epitaxy growth and its heterostructure are still restricted,also for the understanding of its formation mechanism.Herein,we report the stable sublimation of alkali halide vapor assisted synthesis strategy for high-quality 2D HfSe_(2) nanosheets via chemical vapor deposition.Single-crystalline ultrathin 2D HfSe_(2) nanosheets were systematically grown by tuning the growth parameters,reaching the lateral size of 6‒40μm and the thickness down to 4.5 nm.The scalable amorphous HfO_(2)and HfSe_(2)heterostructures were achieved by the controllable oxidation,which benefited from the approximate zero Gibbs free energy of unstable 2D HfSe_(2) templates.The crystal structure,elemental,and time dependent Raman characterization were carried out to understand surface precipitated Se atoms and the formation of amorphous Hf−O bonds,confirming the slow surface oxidation and lattice incorporation of oxygen atoms.The relatively smooth surface roughness and electrical potential change of HfO_(2)−HfSe_(2) heterostructures indicate the excellent interface quality,which helps obtain the high performance memristor with high on/off ratio of 105 and long retention period over 9000 s.Our work introduces a new vapor catalysts strategy for the synthesis of lateral 2D HfSe_(2) nanosheets,also providing the scalable oxidation of the Hf-based heterostructures for 2D electronic devices.展开更多
基金supported by the National Key Research and Development Program of China(2020YFC1909200)the National Natural Science Foundation of China(52104315).
文摘Battery materials as emerging capacitive deionization electrodes for desalination have better salt removal capacities than traditional carbon-based materials.LiMn_(2)O_(4),a widely used cathode mate-rial,is difficult to utilize as a deionization electrode due to its structural instability upon cycling and Mn dissolution in aqueous-based electrolytes.Herein,a facile and low-cost ball-milling routine was proposed to prepare a LiMn_(2)O_(4)material with highly exposed(111)facets.The prepared electrode exhibited relatively low dissolution of Mn during cycling,which shows its long cycle stability.In the hybrid capacitive deionization system,the LiMn_(2)O_(4)/C electrode delivered a high desalination capacity of 117.3 mg g^(−1) without obvious capacity decay at a voltage of 1.0 V with a 20 mM initial salt concentration.In addition,the exposed(111)facets significantly alleviated Mn ion dissolution,which also enhanced the structural steadiness.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11874427 and 11804395)the Fundamental Research Funds for the Central Universities of Central South University (Grant No.2020zzts377)。
文摘Hybrid organic–inorganic perovskite thin films have attracted much attention in optoelectronic and information fields because of their intriguing properties. Due to quantum confinement effects, ultrathin films in nm scale usually show special properties. Here, we report on the growth of methylammonium lead iodide(MAPbI_(3)) ultrathin films via co-deposition of PbI_2 and CH_3NH_3I(MAI) on chemical-vapor-deposition-grown monolayer MoS_(2) as well as the corresponding photoluminescence(PL) properties at different growing stages. Atomic force microscopy and scanning electron microscopy measurements reveal the MoS_(2) tuned growth of MAPbI_(3) in a Stranski–Krastanov mode. PL and Kelvin probe force microscopy results confirm that MAPbI_(3) /MoS_(2) heterostructures have a type-Ⅱ energy level alignment at the interface. Temperaturedependent PL measurements on layered MAPbI_(3) (at the initial stage) and on MAPbI_(3) crystals in averaged size of 500 nm(at the later stage) show rather different temperature dependence as well as the phase transitions from tetragonal to orthorhombic at 120 and 150 K, respectively. Our findings are useful in fabricating MAPbI_(3) /transition-metal dichalcogenide based innovative devices for wider optoelectronic applications.
基金Supported by the National Natural Science Foundation of China(Grant No.51272291)the Distinguished Young Scholar Foundation of Hunan Province(Grant No.2015JJ1020)+3 种基金the Young Scholar Foundation of Hunan Province(Grant No.2016JJ3142)the Central South University Research Fund for Sheng-Hua ScholarsCentral South University State Key Laboratory of Powder Metallurgythe Fundamental Research Funds for the Central Universities of Central South University
文摘Stacking-dependent magnetism in van der Waals materials has caught intense interests.Based on the first principle calculations,we investigate the coupling between stacking orders and interlayer magnetic orders in bilayer H-VSe 2.It is found that there are two stable stacking orders in bilayer H-VSe 2,named AB-stacking and A′B-stacking.Under standard DFT framework,the A′B-stacking prefers the interlayer AFM order and is semiconductive,whereas the AB-stacking prefers the FM order and is metallic.However,under the DFT+U framework both the stacking orders prefer the interlayer AFM order and are semiconductive.By detailedly analyzing this difference,we find that the interlayer magnetism originates from the competition between antiferromagnetic interlayer super-superexchange and ferromagnetic interlayer double exchange,in which both the interlayer Se-4 p z orbitals play a crucial role.In the DFT+U calculations,the double exchange is suppressed due to the opened bandgap,such that the interlayer magnetic orders are decoupled with the stacking orders.Based on this competition mechanism,we propose that a moderate hole doping can significantly enhance the interlayer double exchange,and can be used to switch the interlayer magnetic orders in bilayer VSe 2.This method is also applicable to a wide range of semiconductive van der Waals magnets.
基金supported by the National Natural Science Foundation of China(No.22301158)the Science and Technology Project of Henan Province(No.252102231076).
文摘Developing an effective catalyst for the selective oxidation of hydrocarbon to high value-added compounds remains as a challenge in terms of the growing global concerns about green chemistry and environmental sustainability.Herein,asymmetric nitrogen and phosphorus co-coordinated Ce single-atom sites(Ce-N_(3)P-C)were constructed for the activation of aromatic C-H bond.Ce-N_(3)P-C demonstrates excellent catalytic performance for efficient solvent-free aerobic oxidation of aromatic C-H bonds,especially for oxidation of ethylbenzene with 97%selectivity of acetophenone and high stability.The turnover frequency(TOF)value is 536 h-1,which is the highest level among reported non-precious-metal catalysts in a similar system.The partial substitution of coordinated N with P atom breaks the symmetry of the active moiety of Ce and raises the electron density of Ce center.The reduced valence state of metallic Ce indicates that more electrons could transfer to the antibonding π-orbital of the adsorbed O_(2),thus promoting the subsequent free radical reaction and accelerating the rate-determining step.The breaking of coordination symmetry of single-atom site catalyst by introducing heteroatoms to tune its active moiety paves a way to boost the catalytic performance of similar catalysts.
基金The authors gratefully acknowledge the essential support provided by the National Natural Science Foundation of China(No.52373311)Additional significant contributions are made by the High-Performance Complex Manufacturing Key State Laboratory Project at Central South University(No.ZZYJKT2020-12)+5 种基金the Key Project of the Natural Science Program of the Xinjiang Uygur Autonomous Region(No.2023D01D03)Special thanks are extended to the Australian Research Council for its crucial role in advancing this research(ARC Discovery Project,DP180102976)J.T.Wang also acknowledges support from the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)the National Natural Science Foundation of China(Nos.92263202 and 12374020)the National Key Research and Development Program of China(No.2020YFA0711502)This work is further supported by the Innovation Program for Quantum Science and Technology(No.2021ZD0301605).
文摘Atomically thin two-dimensional(2D)magnetic materials offer unique opportunities to enhance interactions between electron spin,charge,and lattice,leading to novel physical properties at low-dimensional scales.While extensive research has explored how breaking three-fold(Cs)rotational symmetry in transition metal dichalcogenides(TMDC)can induce optical anisotropy at heterointerfaces,the role of magnetism in modulating these anisotropic optical properties remainsunderexplored.anHere,engineerwe antiferromagnet/semiconductor heterostructure by coupling isotropic MoWSe_(2) with the low-symmetric antiferromagnet NiPSs,introducing in-plane anisotropy in the MoWSe_(2) alloy.Low-temperature photoluminescence(PL)measurements reveal a pronounced linear polarization-dependent exciton emission intensity at the MoWSe_(2)/NiPS interface,with anisotropy ratios of 1.09 and 1.07 for charged and neutral excitons,respectively.Furthermore,applying an out-of-plane magnetic field results in a dramatic rotation of the exciton polarization direction by up to 90°at 9 T,significantly exceeding the previously reported maximum deflection of around 27°.This pronounced polarization rotation is not solely attributed to valley coherence,indicating a strong influence of the magnetic order in NiPS3.These findings provide new insights into the role of magnetic ordering in tuning optical anisotropy in 2D materials,paving the way for the development of advanced polarization-sensitive optoelectronic and magneto-optic devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.52073308,12164046,and 12304097)the Key Project of the Natural Science Program of Xinjiang Uygur Autonomous Region(Grant No.2023D01D03)+4 种基金the Tianchi Distinguished Professor Research Fund of Xinjiang Uygur Autonomous Region,the Tianchi-Talent Project for Young Doctors of Xinjiang Uygur Autonomous Region(No.51052300570)China Postdoctoral Science Foundation(Grant Nos.2022TQ0379 and 2023M733972)Hunan Provincial Natural Science Foundation of China(Grant Nos.2023JJ40703 and 2021JJ30864)the Fundamental Research Funds for the Central Universities of Central South University(No.2023ZZTS0385)the State Key Laboratory of Powder Metallurgy at Central South University.
文摘The ferrovalley materials and their nontrivial band topological properties have recently attracted extensive interest in theoretical physics and their promising applications.Using first-principles calculations,we predict the valley polarization in monolayer Mo_(S)nC_(2)S_(6) and MoPbGe_(2)Te_(6).These materials possess a robust ferromagnetic ground state,with high Curie temperatures of 460 K and 319.5 K,respectively.The intrinsic valley polarization arises from the breaking of time-reversal symmetry and spatial inversion symmetry.Biaxial strain and electron correlation(U)can modulate the valley polarization and bandgap.The quantum anomalous Hall phase is driven by biaxial strain and U during the process of bandgap closing,opening,reclosing,and reopening.This can be demonstrated by the chiral edge states at the edges and the plateau in the anomalous Hall conductivity.During the closing and opening of the bandgap,the sign and magnitude of the Berry curvature also vary.Our work provides an ideal platform for valleytronics and the quantum anomalous Hall effect.
基金We acknowledge the financial support from the National Natural Science Foundation of China(NSFC,No.11874427).
文摘Elementary excitations,such as in-plane anisotropic phonons and phonon polaritons(PhPs),inα-MoO_(3) play key roles in its outstanding physical properties like high carrier mobility and ultralow phonon thermal conductivity().Understanding the excitation mechanisms like phonon–phonon interactions is the most fundamental step to further applications.Here,we report on the systematic Raman investigations on phonon anisotropy and anharmonicity of representative Mo–O stretching vibration phonon modes(SVPMs)in physical vapor deposition(PVD)-grownα-MoO_(3) flakes.Polarizations of SVPMs verify the phonon anisotropy.The abnormal temperature dependence of SVPMs reveals that giant quartic-phonon decay dominates the phonon anharmonicity inα-MoO_(3).An ultrashort phonon lifetime of~0.34 ps gives evidence of theoretically predicted ultralow inα-MoO_(3).Our findings give deep insight into the phonon–phonon interactions inα-MoO_(3) and provide an indicator for its extreme thermal device applications.
基金the financial support received from various entities,including the National Natural Science Foundation of China(No.52373311)the Key Project of the Natural Science Program of Xinjiang Uygur Autonomous Region(No.2023D01D03)+4 种基金They also appreciate the support from the High-Performance Complex Manufacturing Key State Lab Project at Central South University(No.ZZYJKT2020-12)ZWL extends thanks to the Australian Research Council(ARC Discovery Project,DP180102976)for their supportJ.-T.W.acknowledges funding from the National Natural Science Foundation of China(Nos.92263202 and 12374020)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)the National Key Research and Development Program of China(No.2020YFA0711502)。
文摘Moiré superlattices based on twisted transition metal dichalcogenide (TMD) heterostructures have recently emerged as a promising platform for probing novel and distinctive electronic phenomena in two-dimensional (2D) materials. By stacking TMD monolayers with a small twist angle, these superlattices create a periodic modulation of the electronic density of states, leading to the formation of mini bands. These mini bands can exhibit intriguing properties such as flat bands, correlated electron behavior, and unconventional superconductivity. This review provides a comprehensive overview of recent progress in Moiré superlattices formed from twisted TMD heterostructures. It covers the theoretical principles and experimental techniques for creating and studying these superlattices, and explores their potential applications in optoelectronics, quantum computing, and energy harvesting. The review also addresses key challenges, such as improving the scalability and reproducibility of the fabrication process, emphasizing the exciting opportunities and ongoing hurdles in this rapidly evolving field.
基金supported by the Science and Technology Innovation Program of Hunan Province(“HuXiang Young Talents”,Grant No.2021RC3021),the Natural Science Foundation of Hunan Province,China(Grant No.2021JJ40780)the National Natural Science Foundation of China(Grant No.51902346)supported by the Open Project Program of Shanxi Key Laboratory of Advanced Semiconductor Optoelectronic Devices and Integrated Systems(Grant No.2023SZKF14).
文摘Two-dimensional transition metal dichalcogenides(TMDs)exhibit promising application prospects in the domains of electronic devices,optoelectronic devices and spintronic devices due to their distinctive energy band structures and spin−orbit coupling properties.Cr-based chalcogenides with narrow or even zero bandgap,covering from semiconductors to metallic materials,have considerable potential for wide-band photodetection and two-dimensional magnetism.Currently,the preparation of 2D CrX_(n)(X=S,Se,Te)nanosheets primarily relies on chemical vapor deposition(CVD)and molecule beam epitaxy(MBE),which enable the production of high-quality large-area materials.This review article focuses on recent progress of 2D Cr-based chalcogenides,including unique crystal structure of the CrX_(n)system,phase-controlled synthesis,and heterojunction construction.Furthermore,a detailed introduction of room-temperature ferromagnetism and electrical/optoelectronic properties of 2D CrXn is presented.Ultimately,this paper summarizes the challenges associated with utilizing 2D Cr-based chalcogenides in preparation strategies,optoelectronics devices,and spintronic devices while providing further insights.
基金the financial support received from various entities,including the National Natural Science Foundation of China(No.52373311)the Key Program of the Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)+5 种基金the Key Project of the Natural Science Program of Xinjiang Uygur Autonomous Region(No.2023D01D03)They also appreciate the support from the High-Performance Complex Manufacturing Key State Lab Project at Central South University(No.ZZYJKT2020-12)Z.W.L.extends thanks to the Australian Research Council(ARC Discovery Project,DP180102976)for their supportJ.-T.W.acknowledges funding from the National Natural Science Foundation of China(Nos.92263202 and 12374020)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)the National Key Research and Development Program of China(No.2020YFA0711502)。
文摘Pressure exerts a profound influence on atomic configurations and interlayer interactions, thereby modulating the electronic and structural properties of materials. While high pressure has been observed to induce a structural phase transition in bulk PdSe_(2) crystals, leading to a transition from semiconductor to metal, the high-pressure behavior of few-layer PdSe_(2) remains elusive. Here, employing diamond anvil cell (DAC) techniques and high-pressure Raman spectroscopy, we investigate the structural evolution of layer-dependent PdSe_(2) under high pressure. We reveal that pressure significantly enhances interlayer coupling in PdSe_(2), driving structural phase transitions from an orthorhombic to a cubic phase. We demonstrate that PdSe_(2) crystals exhibit distinct layer-dependent pressure thresholds during the phase transition, with the decrease of transition pressure as the thickness of PdSe_(2) increases. Furthermore, our results of polarized Raman spectra confirm a reduction in material anisotropy with increasing pressure. This study offers crucial insights into the structural evolution of layer-dependent van der Waals materials under pressure, advancing our understanding of their pressure-induced behaviors.
基金the National Natural Science Foundation of China(Grant Nos.U23A20570 and 51902346)the Science and Technology Innovation Program of Hunan Province(“HuXiang Young Talents”,Grant No.2021RC3021)+1 种基金the Key Project of the Natural Science Program of Xinjiang Uygur Autonomous Region(Grant No.2023D01D03)the Natural Science Foundation of Hunan Province(Grant No.2021JJ40780).
文摘Two-dimensional hafnium-based semiconductors and their heterostructures with native oxides have been shown unique physical properties and potential electronic and optoelectronic applications.However,the scalable synthesis methods for ultrathin layered hafnium-based semiconductor laterally epitaxy growth and its heterostructure are still restricted,also for the understanding of its formation mechanism.Herein,we report the stable sublimation of alkali halide vapor assisted synthesis strategy for high-quality 2D HfSe_(2) nanosheets via chemical vapor deposition.Single-crystalline ultrathin 2D HfSe_(2) nanosheets were systematically grown by tuning the growth parameters,reaching the lateral size of 6‒40μm and the thickness down to 4.5 nm.The scalable amorphous HfO_(2)and HfSe_(2)heterostructures were achieved by the controllable oxidation,which benefited from the approximate zero Gibbs free energy of unstable 2D HfSe_(2) templates.The crystal structure,elemental,and time dependent Raman characterization were carried out to understand surface precipitated Se atoms and the formation of amorphous Hf−O bonds,confirming the slow surface oxidation and lattice incorporation of oxygen atoms.The relatively smooth surface roughness and electrical potential change of HfO_(2)−HfSe_(2) heterostructures indicate the excellent interface quality,which helps obtain the high performance memristor with high on/off ratio of 105 and long retention period over 9000 s.Our work introduces a new vapor catalysts strategy for the synthesis of lateral 2D HfSe_(2) nanosheets,also providing the scalable oxidation of the Hf-based heterostructures for 2D electronic devices.
