Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the la...Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the large-lattice-mismatched and heterovalent semiconductors because of the existing electric field and large strain at the interfaces.Here,we proposed a modified method to calculate band offsets for such systems,in which the core energy level shifts caused by heterovalent effects and lattice mismatch are estimated by interface reconstruction and the insertion of unidirectional strain structures as transitions,respectively.Taking the Si and III-V systems as examples,the results have the same accuracy as what is a widely used method for small-lattice-mismatched systems,and are much closer to the experimental values for the large-lattice-mismatched and heterovalent systems.Furthermore,by systematically studying the heterojunctions of Si and III-V semiconductors along different directions,it is found that the band offsets of Si/InAs and Si/InSb systems in[100],[110]and[111]directions belong to the type I,and could be beneficial for silicon-based luminescence performance.Our study offers a more reliable and direct method for calculating band offsets of large-lattice-mismatched and heterovalent semiconductors,and could provide theoretical support for the design of the high-performance silicon-based light sources.展开更多
Ion bombardment analysis of perovskite materials is challenging owing to their peculiar structure.This shortcoming renders the reliability on the technique somewhat questionable.In this research,three structured modif...Ion bombardment analysis of perovskite materials is challenging owing to their peculiar structure.This shortcoming renders the reliability on the technique somewhat questionable.In this research,three structured modifications(i.e.,scan angle,low energy,and large ion bombardment)were adopted to improve the ion bombardment analysis of 99,999 ions using Monte Carlo simulations.The modified technique was used to analyze the effects of a chemically pressurized‘‘A’’site in the perovskite lattice system.The LaCeTh0.1Cu2Oy compound was used in this experiment.Despite the low probing energy,it was observed that the high number of ions bombarding the material resulted in external pressure on the lattice structure of the material.Moreover,the chemically pressurized‘‘A’’site perovskite material was characterized by lattice mismatch,lattice fluctuations,grain boundary collapse,and oxygen displacement.The novel discovery of this research is the inter-and intra-extended lattice mismatches that are likely to connect.Hence,further investigation of the connection between inter-and intraextended lattice mismatches is recommended as they may enable fabrication of room-temperature superconductors.展开更多
A series of Ti_(56.25-x)Zr_(x)Ni_(25)Cu1_(8.75)(x=0–25,at.%) filler metals were designed based on a cluster-plus-glue-atom model to vacuum braze TiAl intermetallic to K4169 alloy. The impact of Zr content on the inte...A series of Ti_(56.25-x)Zr_(x)Ni_(25)Cu1_(8.75)(x=0–25,at.%) filler metals were designed based on a cluster-plus-glue-atom model to vacuum braze TiAl intermetallic to K4169 alloy. The impact of Zr content on the interfacial microstructure and shear strength of joints was examined. And the relationship between the interfacial lattice structure and the fracture behavior of the joint was investigated. The findings reveal a sectionalized characteristic with three reaction zones (Zone I, Zone II and Zone III) in the microstructure of the TiAl intermetallic to K4169 alloy joint. As the Zr content in filler metals increased, the diffusion of Ti transitioned from long-distance to short-distance in Zone I, changing the initial composition from TiNi_(3) /TiNi/NiNb/(Cr, Fe, Ni)SS to NiCrFe/(Cr, Fe, Ni)SS /TiNi. In Zone II, the initial composition altered from TiNi_(3) /TiNi to TiNi/Ti_(2) Ni/TiNi_(3) /TiCu/TiNi. The interface between Zones II and III altered from a non-coherent and semi-coherent interface of TiNi/TiAl/Ti_(3) Al with significant residual stress to a semi-coherent interface of TiNi/TiNi_(3) /TiAl_(2) /Ti_(3) Al with a gradient distribution. The shear strength of the joint initially decreased and then increased. When the Zr content of filler metal was 25 at.%, the shear strength of the joint reached 288 MPa. The crack initiation position changed from non-coherent TiNi/TiAl interface with high angle grain boundaries (HAGBs) and lattice mismatch of 65.86 at.% to a semi-coherent Ti3 Al/TiAl2 interface with a lattice mismatch of 20.07 at.% when the Zr content increased. The brittle fracture was present on the fracture surfaces of all brazed joints.展开更多
Organic heterostructures(OHSs)consist of organic micro/nanocrystals are of essential importance for the construction of integrated optoelectronics in the future.However,the scarcity of materials and the problem of pha...Organic heterostructures(OHSs)consist of organic micro/nanocrystals are of essential importance for the construction of integrated optoelectronics in the future.However,the scarcity of materials and the problem of phase separation still hinder the fine synthesis of OHSs.Herein,based on theαphase one-dimensional(1D)microrods and theβphase 2D microplates of one organic compound 3,3′-((1 E,1′E)-anthracene-9,10-diylbis(ethane-2,1-diyl))dibenzonitril(m-B2BCB),we facilely synthesized the OHSs composed of these two polymorph phases,whose growth mechanism is attributed to the low lattice mismatch rate of5.8%between(001)plane ofαphase(trunk)and(010)crystal plane ofβphase(branch).Significantly,the multiport in/output channels can be achieved in the OHSs,which demonstrates the structure-dependent optical signals with the different output channels in the OHSs.Therefore,our experiment exhibits the great prospect of polymorphism in OHSs,which could provide further applications on multifunctional organic integrated photonics circuits.展开更多
Effective charge separation and transfer is deemed to be the contributing factor to achieve high photoelectrochemical(PEC)water splitting performance on photoelectrodes.Building a phase junction structure with control...Effective charge separation and transfer is deemed to be the contributing factor to achieve high photoelectrochemical(PEC)water splitting performance on photoelectrodes.Building a phase junction structure with controllable phase transition of WO_(3) can further improve the photocatalytic performance.In this work,we realized the transition from orthorhombic to monoclinic by regulating the annealing temperatures,and constructed an orthorhombic–monoclinic WO_(3)(o-WO_(3)/m-WO_(3))phase junction.The formation of oxygen vacancies causes an imbalance of the charge distribution in the crystal structure,which changes the W–O bond length and bond angle,accelerating the phase transition.As expected,an optimum PEC activity was achieved over the o-WO_(3)/m-WO_(3) phase junction in WO_(3)-450 photoelectrode,yielding the maximum O_(2) evolution rate roughly 32 times higher than that of pure WO_(3)-250 without any sacrificial agents under visible light irradiation.The enhancement of catalytic activity is attributed to the atomically smooth interface with a highly matched lattice and robust built-in electric field around the phase junction,which leads to a less-defective and abrupt interface and provides a smooth interfacial charge separation and transfer path,leading to improved charge separation and transfer efficiency and a great enhancement in photocatalytic activity.This work strikes out on new paths in the formation of an oxygen vacancy-induced phase transition and provides new ideas for the design of catalysts.展开更多
YBa_(2)Cu_(3)O_(7‐x)(YBCO)thin films were prepared on LaAlO_(3)(LAO)substrates by a sol–gel method,and the epitaxial growth of Bi‐2212 thin films on YBCO thin films was investigated.Both YBCO and Bi_(2)Sr_(2)Ca1Cu_...YBa_(2)Cu_(3)O_(7‐x)(YBCO)thin films were prepared on LaAlO_(3)(LAO)substrates by a sol–gel method,and the epitaxial growth of Bi‐2212 thin films on YBCO thin films was investigated.Both YBCO and Bi_(2)Sr_(2)Ca1Cu_(2)O_(8)+δ(Bi‐2212)bilayer films exhibit good biaxial texture and superconducting properties.Afterward,a cross‐shaped Bi‐2212/YBCO heterostructure was fabricated,and its interfacial atomic arrangement and I‐V characteristics were analyzed.Atomic‐resolution STEM images obtained from a spherical‐aberration‐corrected transmission electron microscope show that two superconducting films exhibit a layered structure and the atoms inside the films are artfully arranged.Moreover,the order of the seven atomic layers between Bi‐2212 and YBCO layers with a thickness of about 1.32 nm is misarranged.Among them,the Y‐O layer of YBCO and the Sr‐O layer of Bi‐2212 share a CuO_(2) layer.The I‐V curves of Bi‐2212/YBCO bilayer films show that the seven misarranged atomic layers at Bi‐2212/YBCO interface acts as a barrier layer,which means that a Josephson junction can be fabricated using this interface characters.展开更多
Strain engineering,as a cutting-edge method for modulating the electronic structure of catalysts,plays a crucial role in regulating the interaction between the catalytic surface and the adsorbed molecules.The electroc...Strain engineering,as a cutting-edge method for modulating the electronic structure of catalysts,plays a crucial role in regulating the interaction between the catalytic surface and the adsorbed molecules.The electrocatalytic performance is influenced by the electronic structure,which can be achieved by introducing the external forces or stresses to adjust interatomic spacing between surface atoms.The challenges in strain engineering research lie in accurately understanding the mechanical impact of strain on performance.This paper first introduces the basic strategy for generating the strain,summarizes the different strain generation forms and their advantages and disadvantages.The progress in researching the characterization means for the lattice strains and their applications in the field of electrocatalysis is also emphasized.Finally,the challenges of strain engineering are introduced,and an outlook on the future research directions is provided.展开更多
基金This work was supported by the National Key Research and Development Program of China(Grant No.2018YFB2200100)the Key Research Program of the Chinese Academy of Sciences(Grant No.XDPB22)+1 种基金the National Natural Science Foundation of China(Grant No.118764347,11614003,11804333)H.X.D.was also supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2017154).
文摘Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices.However,the current method of calculating band offset is difficult to apply directly to the large-lattice-mismatched and heterovalent semiconductors because of the existing electric field and large strain at the interfaces.Here,we proposed a modified method to calculate band offsets for such systems,in which the core energy level shifts caused by heterovalent effects and lattice mismatch are estimated by interface reconstruction and the insertion of unidirectional strain structures as transitions,respectively.Taking the Si and III-V systems as examples,the results have the same accuracy as what is a widely used method for small-lattice-mismatched systems,and are much closer to the experimental values for the large-lattice-mismatched and heterovalent systems.Furthermore,by systematically studying the heterojunctions of Si and III-V semiconductors along different directions,it is found that the band offsets of Si/InAs and Si/InSb systems in[100],[110]and[111]directions belong to the type I,and could be beneficial for silicon-based luminescence performance.Our study offers a more reliable and direct method for calculating band offsets of large-lattice-mismatched and heterovalent semiconductors,and could provide theoretical support for the design of the high-performance silicon-based light sources.
基金partial sponsorship of the Covenant University,Nigeria,and University of Johannesburg
文摘Ion bombardment analysis of perovskite materials is challenging owing to their peculiar structure.This shortcoming renders the reliability on the technique somewhat questionable.In this research,three structured modifications(i.e.,scan angle,low energy,and large ion bombardment)were adopted to improve the ion bombardment analysis of 99,999 ions using Monte Carlo simulations.The modified technique was used to analyze the effects of a chemically pressurized‘‘A’’site in the perovskite lattice system.The LaCeTh0.1Cu2Oy compound was used in this experiment.Despite the low probing energy,it was observed that the high number of ions bombarding the material resulted in external pressure on the lattice structure of the material.Moreover,the chemically pressurized‘‘A’’site perovskite material was characterized by lattice mismatch,lattice fluctuations,grain boundary collapse,and oxygen displacement.The novel discovery of this research is the inter-and intra-extended lattice mismatches that are likely to connect.Hence,further investigation of the connection between inter-and intraextended lattice mismatches is recommended as they may enable fabrication of room-temperature superconductors.
基金supported by the National Natural Science Foundation of China(52173177 and 21971185)the Natural Science Foundation of Jiangsu Province(BK20221362)+5 种基金the Science and Technology Support Program of Jiangsu Province(TJ-2022-002)supported by Suzhou Key Laboratory of Functional Nano&Soft Materialsthe Collaborative Innovation Center of Suzhou Nano Science&Technologythe 111 Projectthe Joint International Research Laboratory of Carbon-Based Functional Materials and DevicesSoochow University Tang Scholar。
基金supported by the National Natural Science Foun-dation of China(Nos.52275314 and 52075074)the Collaborative Innovation Center of Major Machine Manufacturing in Liaoning.
文摘A series of Ti_(56.25-x)Zr_(x)Ni_(25)Cu1_(8.75)(x=0–25,at.%) filler metals were designed based on a cluster-plus-glue-atom model to vacuum braze TiAl intermetallic to K4169 alloy. The impact of Zr content on the interfacial microstructure and shear strength of joints was examined. And the relationship between the interfacial lattice structure and the fracture behavior of the joint was investigated. The findings reveal a sectionalized characteristic with three reaction zones (Zone I, Zone II and Zone III) in the microstructure of the TiAl intermetallic to K4169 alloy joint. As the Zr content in filler metals increased, the diffusion of Ti transitioned from long-distance to short-distance in Zone I, changing the initial composition from TiNi_(3) /TiNi/NiNb/(Cr, Fe, Ni)SS to NiCrFe/(Cr, Fe, Ni)SS /TiNi. In Zone II, the initial composition altered from TiNi_(3) /TiNi to TiNi/Ti_(2) Ni/TiNi_(3) /TiCu/TiNi. The interface between Zones II and III altered from a non-coherent and semi-coherent interface of TiNi/TiAl/Ti_(3) Al with significant residual stress to a semi-coherent interface of TiNi/TiNi_(3) /TiAl_(2) /Ti_(3) Al with a gradient distribution. The shear strength of the joint initially decreased and then increased. When the Zr content of filler metal was 25 at.%, the shear strength of the joint reached 288 MPa. The crack initiation position changed from non-coherent TiNi/TiAl interface with high angle grain boundaries (HAGBs) and lattice mismatch of 65.86 at.% to a semi-coherent Ti3 Al/TiAl2 interface with a lattice mismatch of 20.07 at.% when the Zr content increased. The brittle fracture was present on the fracture surfaces of all brazed joints.
基金supported by the National Natural Science Foundation of China(21703148,21971185)the Natural Science Foundation of Jiangsu Province(BK20170330)+2 种基金the Collaborative Innovation Center of Suzhou Nano Science and Technology(CIC-Nano)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the“111”Project of the State Administration of Foreign Experts Affairs of China。
文摘Organic heterostructures(OHSs)consist of organic micro/nanocrystals are of essential importance for the construction of integrated optoelectronics in the future.However,the scarcity of materials and the problem of phase separation still hinder the fine synthesis of OHSs.Herein,based on theαphase one-dimensional(1D)microrods and theβphase 2D microplates of one organic compound 3,3′-((1 E,1′E)-anthracene-9,10-diylbis(ethane-2,1-diyl))dibenzonitril(m-B2BCB),we facilely synthesized the OHSs composed of these two polymorph phases,whose growth mechanism is attributed to the low lattice mismatch rate of5.8%between(001)plane ofαphase(trunk)and(010)crystal plane ofβphase(branch).Significantly,the multiport in/output channels can be achieved in the OHSs,which demonstrates the structure-dependent optical signals with the different output channels in the OHSs.Therefore,our experiment exhibits the great prospect of polymorphism in OHSs,which could provide further applications on multifunctional organic integrated photonics circuits.
基金The financial support is gratefully acknowledged from the National Natural Science Foundation of China(Grant Nos.62004137,21878257,and 21978196)Natural Science Foundation of Shanxi Province(Grant No.20210302123102)+4 种基金Key Research and Development Program of Shanxi Province(Grant No.201803D421079)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2019L0156)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(Grant No.2022SX-TD002)Shanxi Provincial Key Innovative Research Team in Science and Technology(Grant No.201605D13104510)Research Project Supported by Shanxi Scholarship Council of China(Grant No.2020-050).
文摘Effective charge separation and transfer is deemed to be the contributing factor to achieve high photoelectrochemical(PEC)water splitting performance on photoelectrodes.Building a phase junction structure with controllable phase transition of WO_(3) can further improve the photocatalytic performance.In this work,we realized the transition from orthorhombic to monoclinic by regulating the annealing temperatures,and constructed an orthorhombic–monoclinic WO_(3)(o-WO_(3)/m-WO_(3))phase junction.The formation of oxygen vacancies causes an imbalance of the charge distribution in the crystal structure,which changes the W–O bond length and bond angle,accelerating the phase transition.As expected,an optimum PEC activity was achieved over the o-WO_(3)/m-WO_(3) phase junction in WO_(3)-450 photoelectrode,yielding the maximum O_(2) evolution rate roughly 32 times higher than that of pure WO_(3)-250 without any sacrificial agents under visible light irradiation.The enhancement of catalytic activity is attributed to the atomically smooth interface with a highly matched lattice and robust built-in electric field around the phase junction,which leads to a less-defective and abrupt interface and provides a smooth interfacial charge separation and transfer path,leading to improved charge separation and transfer efficiency and a great enhancement in photocatalytic activity.This work strikes out on new paths in the formation of an oxygen vacancy-induced phase transition and provides new ideas for the design of catalysts.
基金supported by the National Natural Science Foundation of China(52172273 and 51672212)the Key Science and Technology Program of Shaanxi Province of China(No.2020zdzx04‐04‐02).
文摘YBa_(2)Cu_(3)O_(7‐x)(YBCO)thin films were prepared on LaAlO_(3)(LAO)substrates by a sol–gel method,and the epitaxial growth of Bi‐2212 thin films on YBCO thin films was investigated.Both YBCO and Bi_(2)Sr_(2)Ca1Cu_(2)O_(8)+δ(Bi‐2212)bilayer films exhibit good biaxial texture and superconducting properties.Afterward,a cross‐shaped Bi‐2212/YBCO heterostructure was fabricated,and its interfacial atomic arrangement and I‐V characteristics were analyzed.Atomic‐resolution STEM images obtained from a spherical‐aberration‐corrected transmission electron microscope show that two superconducting films exhibit a layered structure and the atoms inside the films are artfully arranged.Moreover,the order of the seven atomic layers between Bi‐2212 and YBCO layers with a thickness of about 1.32 nm is misarranged.Among them,the Y‐O layer of YBCO and the Sr‐O layer of Bi‐2212 share a CuO_(2) layer.The I‐V curves of Bi‐2212/YBCO bilayer films show that the seven misarranged atomic layers at Bi‐2212/YBCO interface acts as a barrier layer,which means that a Josephson junction can be fabricated using this interface characters.
基金supported by the National Natural Science Foundation of China(Nos.12172118,52071125,12227801)the Research Program of Local Science and Technology Development under the Guidance of Central(No.216Z4402G)+2 种基金Science Research Project of Hebei Education Department(No.JZX2023004)Opening fund of State Key Laboratory of Nonlinear Mechanics(LNM)National Key Research and Development Program of China(No.2019YFC0840709)。
文摘Strain engineering,as a cutting-edge method for modulating the electronic structure of catalysts,plays a crucial role in regulating the interaction between the catalytic surface and the adsorbed molecules.The electrocatalytic performance is influenced by the electronic structure,which can be achieved by introducing the external forces or stresses to adjust interatomic spacing between surface atoms.The challenges in strain engineering research lie in accurately understanding the mechanical impact of strain on performance.This paper first introduces the basic strategy for generating the strain,summarizes the different strain generation forms and their advantages and disadvantages.The progress in researching the characterization means for the lattice strains and their applications in the field of electrocatalysis is also emphasized.Finally,the challenges of strain engineering are introduced,and an outlook on the future research directions is provided.