The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magne...The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magnetic semiconductor families, including europium chalcogenides, chromium spinels, dilute magnetic semiconductors, dilute ferromagnetic semiconductors and insulators, mentioning also sources of non-uniformities in the magnetization distribution, accounting for an apparent high Curie temperature ferromagnetism in many systems. Our survey is carried out from today's perspective of ferromagnetic and antiferromagnetic spintronics as well as of the emerging fields of magnetic topological materials and atomically thin 2D layers.展开更多
Hexagonal boron nitride nanosheets(HBNNSs)have huge potential in the field of coating materials owing to their remarkable chemical stability,mechanical strength and thermal conductivity.Thin-layer hBNNSs were obtained...Hexagonal boron nitride nanosheets(HBNNSs)have huge potential in the field of coating materials owing to their remarkable chemical stability,mechanical strength and thermal conductivity.Thin-layer hBNNSs were obtained by a liquid-phase exfoliation of h-BN powders and incorporated into EVA coatings for improving the safety performance of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX).HBNNSs and ethylene-vinyl acetate copolymer(EVA)were introduced to HMX by a solvent-slurry process.For comparison,the HMX/EVA and HMX/EVA/graphene(HMX/EVA/G)composites were also prepared by a similar process.The morphology,crystal form,surface element distribution,thermal decomposition property and impact sensitivity of HMX/EVA/hBNNSs composites were contrastively investigated.Results showed that as prepared HMX/EVA/hBNNSs composites were well coated with hBNNSs and EVA,and exhibited better thermal stability and lower impact sensitivity than that of HMX/EVA and HMX/EVA/G composites,suggesting superior performance of desensitization of hBNNSs in explosives.展开更多
By means of density functional theory computations, we predicted two novel two-dimensional （2D） nanolnaterials, namely P2X （X=C, Si） monolayers with pentagonal configurations. Their structures, stabilities, intrin...By means of density functional theory computations, we predicted two novel two-dimensional （2D） nanolnaterials, namely P2X （X=C, Si） monolayers with pentagonal configurations. Their structures, stabilities, intrinsic electronic, and optical properties as well as the effect of external strain to the elec- tronic properties have been systematically examined. Our computations showed that these P2C and P2Si monolayers have rather high thermodynamic, kinetic, and thermal stabilities, and are indirect semiconductors with wide bandgaps （2.76 eV and 2.69 eV, respectively） which can be tuned by an external strain. These monolayers exhibit high absorptions in the UV region, but behave as almost transparent layers for visible light in the electromagnetic spectrum. Their high stabilities and excep- tional electronic and optical properties suggest them as promising candidates for future applications in UV-light shielding and antireflection layers in solar cells.展开更多
By means of density functional theory （DFT） computations and particle-swarm optimization （PSO） structure searches, we herein predict five low-lying energy structures of two-dimensional （2D） aluminum monoxide （...By means of density functional theory （DFT） computations and particle-swarm optimization （PSO） structure searches, we herein predict five low-lying energy structures of two-dimensional （2D） aluminum monoxide （AIO） nanosheets. Their high cohesive energy, absence of imaginary phonon dispersion, and good thermal stability make them feasible targets for experimental realization. These monolayers exhibit diverse structural topologies, for instance, PmA- and Pmm-A10 possess buckled four- and six- membered A10 rings, whereas P62-, PmB-, and P6m-A10 have pores of varied sizes. Interestingly, the most energetically preferred monolayers, PmA- and Pmm-A10, feature wide band gaps （2.45 and 5.13 eV, respectively）, which are promising for green and blue light-emitting devices （LEDs） and photodetectors.展开更多
As a two-dimensional carbon based semiconductor,C_(3)N acts as a promising material in many application areas.However,the basic physical properties such as Raman spectrum properties of C_(3)N is still not clear.In thi...As a two-dimensional carbon based semiconductor,C_(3)N acts as a promising material in many application areas.However,the basic physical properties such as Raman spectrum properties of C_(3)N is still not clear.In this paper,we clarify the Raman spectrum properties of multilayer C_(3)N.Moreover,the stacking driven Raman spectra change of multilayer C_(3)N is also discussed.展开更多
Two-dimensional transition metal dichalcogenide semiconductors have emerged as promising candidates for optoelectronic devices with unprecedented properties and ultra-compact footprints. However, the high sensitivity ...Two-dimensional transition metal dichalcogenide semiconductors have emerged as promising candidates for optoelectronic devices with unprecedented properties and ultra-compact footprints. However, the high sensitivity of atomically thin materials to the surrounding dielectric media imposes severe limitations on their practical applicability. Hence, to enable the effective integration of these materials in devices, the development of reliable encapsulation procedures that preserve their physical properties is required. Here, the excitonic photoluminescence （at room temperature and 10 K） is assessed on mechanically exfoliated WSe2 monolayer flakes encapsulated with SiOx and AlxOy layers by means of chemical and physical deposition techniques. Conformal coating on untreated and non- functionalized flakes is successfully achieved by all the techniques examined, with the exception of atomic layer deposition, for which a cluster-like oxide coating is formed. No significant compositional or strain state changes in the flakes are detected upon encapsulation, independently of the technique adopted. Remarkably, our results show that the optical emission of the flakes is strongly influenced by the stoichiometry quality of the encapsulating oxide. When the encapsulation is carried out with slightly sub-stoichiometric oxides, two remarkable phenomena are observed. First, dominant trion （charged exciton） photoluminescence is detected at room temperature, revealing a clear electrical doping of the monolayers. Second, a strong decrease in the optical emission of the monolayers is observed, and attributed to non-radiative recombination processes and/or carrier transfer from the flake to the oxide. Power- and temperature-dependent photoluminescence measurements further confirm that stoichiometric oxides obtained by physical deposition lead to a successful encapsulation, opening a promising route for the development of integrated two-dimensional devices.展开更多
The field of two-dimensional(2D)materials has stimulated considerable interest in the scientific community.Owing to quantum confinement in one direction,intriguing properties have been reported in 2D materials that ca...The field of two-dimensional(2D)materials has stimulated considerable interest in the scientific community.Owing to quantum confinement in one direction,intriguing properties have been reported in 2D materials that cannot be observed in their bulk form.The advent of semiconducting 2D materials with a broad range of electronic properties has provided fascinating opportunities to design and configure next-generation electronics.One such emerging class is the family of III-VI monochalcogenides,the two prominent members of which are indium selenide(InSe)and gallium selenide(GaSe).In contrast to transition metal dichalcogenides,their high intrinsic mobility and the availability of a direct bandgap at small thicknesses have attracted researchers to investigate the underlying physical phenomena as well as their technological applications.However,the sensitivity of InSe and GaSe to environmental influences has limited their exploitation in functional devices.The lack of methods for their scalable synthesis further hinders the realization of their devices.This review article outlines recent advancements in the synthesis and understanding of the charge transport properties of InSe and GaSe for their integration into technological applications.A detailed summary of the improvements in the device structure by optimizing extrinsic factors such as bottom substrates,metal contacts,and device fabrication schemes is provided.Furthermore,various encapsulation techniques that have been proven effective in preventing the degradation of InSe and GaSe layers under ambient conditions are thoroughly discussed.Finally,this article presents an outlook on future research ventures with respect to ongoing developments and practical viability of these materials.展开更多
In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic stru...In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic structure. With the development of the synthesis and modification methods of BP, its extensive applications, e.g., transistors, batteries and optoelectronics have emerged. In order to explore its full potential, research into the tribological properties of BP 2D-layered materials such as lubrication additives and fillers in self-lubricating composite materials would be not only of high scientific value but also of practical significance. In this work, recent advances on the friction and lubrication properties of BP nanosheets made by our group, including the micro-friction properties, the lubrication properties of BP nanosheets as water-based and oil-based lubrication additives, and the friction and wear of BP/PVDF composites will be presented. Finally, the future challenges and opportunities in the use of BP materials as lubricants will be discussed.展开更多
基金supported by the Foundation for Polish Science through the IRA Programme financed by EU within SG OP Programmesupport by the Austrian Science Foundation-FWF (P31423 and P26830)the Austrian Exchange Service (OAD) Project PL-01/2017
文摘The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magnetic semiconductor families, including europium chalcogenides, chromium spinels, dilute magnetic semiconductors, dilute ferromagnetic semiconductors and insulators, mentioning also sources of non-uniformities in the magnetization distribution, accounting for an apparent high Curie temperature ferromagnetism in many systems. Our survey is carried out from today's perspective of ferromagnetic and antiferromagnetic spintronics as well as of the emerging fields of magnetic topological materials and atomically thin 2D layers.
基金The project was supported by Equipment Pre-research Key Laboratory Fund(No.6142020305)The authors would like to thank Shiyanjia Lab(www.shiyanjia.com)for the support of XPS test.
文摘Hexagonal boron nitride nanosheets(HBNNSs)have huge potential in the field of coating materials owing to their remarkable chemical stability,mechanical strength and thermal conductivity.Thin-layer hBNNSs were obtained by a liquid-phase exfoliation of h-BN powders and incorporated into EVA coatings for improving the safety performance of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX).HBNNSs and ethylene-vinyl acetate copolymer(EVA)were introduced to HMX by a solvent-slurry process.For comparison,the HMX/EVA and HMX/EVA/graphene(HMX/EVA/G)composites were also prepared by a similar process.The morphology,crystal form,surface element distribution,thermal decomposition property and impact sensitivity of HMX/EVA/hBNNSs composites were contrastively investigated.Results showed that as prepared HMX/EVA/hBNNSs composites were well coated with hBNNSs and EVA,and exhibited better thermal stability and lower impact sensitivity than that of HMX/EVA and HMX/EVA/G composites,suggesting superior performance of desensitization of hBNNSs in explosives.
文摘By means of density functional theory computations, we predicted two novel two-dimensional （2D） nanolnaterials, namely P2X （X=C, Si） monolayers with pentagonal configurations. Their structures, stabilities, intrinsic electronic, and optical properties as well as the effect of external strain to the elec- tronic properties have been systematically examined. Our computations showed that these P2C and P2Si monolayers have rather high thermodynamic, kinetic, and thermal stabilities, and are indirect semiconductors with wide bandgaps （2.76 eV and 2.69 eV, respectively） which can be tuned by an external strain. These monolayers exhibit high absorptions in the UV region, but behave as almost transparent layers for visible light in the electromagnetic spectrum. Their high stabilities and excep- tional electronic and optical properties suggest them as promising candidates for future applications in UV-light shielding and antireflection layers in solar cells.
基金This work was supported by the Na.tional Science Foundation-Centers of Research Excellence in Science and Technology （NSF-CREST Center） for Innovation, Research and Education in Environmental Nanotechnology （CIRE2N） （Grant No. HRD-1736093） and NASA （Grant No. 17-EPSCoRProp-0032）.
文摘By means of density functional theory （DFT） computations and particle-swarm optimization （PSO） structure searches, we herein predict five low-lying energy structures of two-dimensional （2D） aluminum monoxide （AIO） nanosheets. Their high cohesive energy, absence of imaginary phonon dispersion, and good thermal stability make them feasible targets for experimental realization. These monolayers exhibit diverse structural topologies, for instance, PmA- and Pmm-A10 possess buckled four- and six- membered A10 rings, whereas P62-, PmB-, and P6m-A10 have pores of varied sizes. Interestingly, the most energetically preferred monolayers, PmA- and Pmm-A10, feature wide band gaps （2.45 and 5.13 eV, respectively）, which are promising for green and blue light-emitting devices （LEDs） and photodetectors.
基金supported by The National Natural Science Foundation of China (Nos. 11804353 and 11774368)Shanghai Science and Technology Committee (No. 18511110600)
文摘As a two-dimensional carbon based semiconductor,C_(3)N acts as a promising material in many application areas.However,the basic physical properties such as Raman spectrum properties of C_(3)N is still not clear.In this paper,we clarify the Raman spectrum properties of multilayer C_(3)N.Moreover,the stacking driven Raman spectra change of multilayer C_(3)N is also discussed.
基金The authors would like to thank Georgios Katsaros and Tim Wehling for valuable discussions. Stephan Br~iuer, Albin Schwarz, and Ursula Kainz are ackno- wledged for technical support. A. M. acknowledges the financial support through BES-2013-062593. G. G. acknowledges support from the Austrian Science Fund through project P 28018-B27. I. Z. acknowledges financial support from the Swiss National Science Foundation research grant （No. 200021_165784）. This work was partially funded by the Austrian Science Fund through the projects P24471 and P26830, and by the Spanish Ministry for Economy and Competitiveness trough the project MINECO/FEDER TEC2015-69916- C2-1-R.
文摘Two-dimensional transition metal dichalcogenide semiconductors have emerged as promising candidates for optoelectronic devices with unprecedented properties and ultra-compact footprints. However, the high sensitivity of atomically thin materials to the surrounding dielectric media imposes severe limitations on their practical applicability. Hence, to enable the effective integration of these materials in devices, the development of reliable encapsulation procedures that preserve their physical properties is required. Here, the excitonic photoluminescence （at room temperature and 10 K） is assessed on mechanically exfoliated WSe2 monolayer flakes encapsulated with SiOx and AlxOy layers by means of chemical and physical deposition techniques. Conformal coating on untreated and non- functionalized flakes is successfully achieved by all the techniques examined, with the exception of atomic layer deposition, for which a cluster-like oxide coating is formed. No significant compositional or strain state changes in the flakes are detected upon encapsulation, independently of the technique adopted. Remarkably, our results show that the optical emission of the flakes is strongly influenced by the stoichiometry quality of the encapsulating oxide. When the encapsulation is carried out with slightly sub-stoichiometric oxides, two remarkable phenomena are observed. First, dominant trion （charged exciton） photoluminescence is detected at room temperature, revealing a clear electrical doping of the monolayers. Second, a strong decrease in the optical emission of the monolayers is observed, and attributed to non-radiative recombination processes and/or carrier transfer from the flake to the oxide. Power- and temperature-dependent photoluminescence measurements further confirm that stoichiometric oxides obtained by physical deposition lead to a successful encapsulation, opening a promising route for the development of integrated two-dimensional devices.
基金Initiative and Networking Fund of the Helmholtz Association of German Research Centers,Grant/Award Number:VH-KO-606。
文摘The field of two-dimensional(2D)materials has stimulated considerable interest in the scientific community.Owing to quantum confinement in one direction,intriguing properties have been reported in 2D materials that cannot be observed in their bulk form.The advent of semiconducting 2D materials with a broad range of electronic properties has provided fascinating opportunities to design and configure next-generation electronics.One such emerging class is the family of III-VI monochalcogenides,the two prominent members of which are indium selenide(InSe)and gallium selenide(GaSe).In contrast to transition metal dichalcogenides,their high intrinsic mobility and the availability of a direct bandgap at small thicknesses have attracted researchers to investigate the underlying physical phenomena as well as their technological applications.However,the sensitivity of InSe and GaSe to environmental influences has limited their exploitation in functional devices.The lack of methods for their scalable synthesis further hinders the realization of their devices.This review article outlines recent advancements in the synthesis and understanding of the charge transport properties of InSe and GaSe for their integration into technological applications.A detailed summary of the improvements in the device structure by optimizing extrinsic factors such as bottom substrates,metal contacts,and device fabrication schemes is provided.Furthermore,various encapsulation techniques that have been proven effective in preventing the degradation of InSe and GaSe layers under ambient conditions are thoroughly discussed.Finally,this article presents an outlook on future research ventures with respect to ongoing developments and practical viability of these materials.
基金support of the National Natural Science Foundation of China(Grant Nos.51527901,51335005,51475256,and 51605249)
文摘In recent years, a new 2D-layered material—black phosphorus(BP)—has been a rising star after the era of graphene owing to its high charge carrier mobility, tunable direct bandgap and unique in-plane anisotropic structure. With the development of the synthesis and modification methods of BP, its extensive applications, e.g., transistors, batteries and optoelectronics have emerged. In order to explore its full potential, research into the tribological properties of BP 2D-layered materials such as lubrication additives and fillers in self-lubricating composite materials would be not only of high scientific value but also of practical significance. In this work, recent advances on the friction and lubrication properties of BP nanosheets made by our group, including the micro-friction properties, the lubrication properties of BP nanosheets as water-based and oil-based lubrication additives, and the friction and wear of BP/PVDF composites will be presented. Finally, the future challenges and opportunities in the use of BP materials as lubricants will be discussed.
