Based on the principle of thermal conduction, three metal alloys (stainless steel, copper-tungsten and graphite) were chosen as the material of the high impulse current discharging switch. Experimental results indic...Based on the principle of thermal conduction, three metal alloys (stainless steel, copper-tungsten and graphite) were chosen as the material of the high impulse current discharging switch. Experimental results indicate that the mass loss and surface erosion morphology of the electrode are related with the electrode material (conductivity σ, melting point Tin, density p and thermal capacity c) and the impulse transferred charge (or energy) per impulse for the same total impulse transferred charge. The experimental results indicate that the mass loss of stainless steel, copper-tungsten and graphite are 380.10 μg/C, 118.10 μg/C and 81.90 μg/C respectively under the condition of a total impulse transferred charge of 525 C and a transferred charge per impulse of 10.5 C. Under the same impulse transferred charge, the mass loss of copper-tungsten(118.10 μg/C) with the transferred charge per impulse at 10.5 C is far larger than the mass loss (38.61μg/C) at a 1.48 C transferred charge per impulse. The electrode erosion mechanism under high energy impulse arcs is analyzed briefly and it is suggested that by selecting high conductive metal or metal alloy as the electrode material of a high energy impulse spark gap switch and setting high erosion resistance material at the top of the electrode, the mass loss of the electrode can be reduced and the life of the switch prolonged.展开更多
Van der Waals heterojunctions are fast-emerging quantum structures fabricated by the controlled stacking of two-dimensional(2D)materials.Owing to the atomically thin thickness,their carrier properties are not only det...Van der Waals heterojunctions are fast-emerging quantum structures fabricated by the controlled stacking of two-dimensional(2D)materials.Owing to the atomically thin thickness,their carrier properties are not only determined by the host material itself,but also defined by the interlayer interactions,including dielectric environment,charge trapping centers,and stacking angles.The abundant constituents without the limitation of lattice constant matching enable fascinating electrical,optical,and magnetic properties in van der Waals heterojunctions toward next-generation devices in photonics,optoelectronics,and information sciences.This review focuses on the charge and energy transfer processes and their dynamics in transition metal dichalcogenides(TMDCs),a family of quantum materials with strong excitonic effects and unique valley properties,and other related 2D materials such as graphene and hexagonalboron nitride.In the first part,we summarize the ultrafast charge transfer processes in van der Waals heterojunctions,including its experimental evidence and theoretical understanding,the interlayer excitons at the TMDC interfaces,and the hot carrier injection at the graphene/TMDCs interface.In the second part,the energy transfer,including both Förster and Dexter types,are reviewed from both experimental and theoretical perspectives.Finally,we highlight the typical charge and energy transfer applications in photodetectors and summarize the challenges and opportunities for future development in this field.展开更多
Efficient electronic coupling is the key to constructing optoelectronic functionalπsystems.Generally,the delocalization ofπelectrons must comply with the framework constructed by covalent bonds(typicallyσbonds),rep...Efficient electronic coupling is the key to constructing optoelectronic functionalπsystems.Generally,the delocalization ofπelectrons must comply with the framework constructed by covalent bonds(typicallyσbonds),representing classic through-bond conjuga-tion.However,through-space conjugation offers an alternative that achieves spatial electron communica-tionwith closely stacked π systems instead of covalent bonds thus enabling multidimensional energy and charge transport.展开更多
文摘Based on the principle of thermal conduction, three metal alloys (stainless steel, copper-tungsten and graphite) were chosen as the material of the high impulse current discharging switch. Experimental results indicate that the mass loss and surface erosion morphology of the electrode are related with the electrode material (conductivity σ, melting point Tin, density p and thermal capacity c) and the impulse transferred charge (or energy) per impulse for the same total impulse transferred charge. The experimental results indicate that the mass loss of stainless steel, copper-tungsten and graphite are 380.10 μg/C, 118.10 μg/C and 81.90 μg/C respectively under the condition of a total impulse transferred charge of 525 C and a transferred charge per impulse of 10.5 C. Under the same impulse transferred charge, the mass loss of copper-tungsten(118.10 μg/C) with the transferred charge per impulse at 10.5 C is far larger than the mass loss (38.61μg/C) at a 1.48 C transferred charge per impulse. The electrode erosion mechanism under high energy impulse arcs is analyzed briefly and it is suggested that by selecting high conductive metal or metal alloy as the electrode material of a high energy impulse spark gap switch and setting high erosion resistance material at the top of the electrode, the mass loss of the electrode can be reduced and the life of the switch prolonged.
基金Agency for Science,Technology and Research,Grant/Award Number:1527300025Central University Basic Research Fund of China,Grant/Award Numbers:020514380231,021014380177+5 种基金National Natural Science Foundation of China,Grant/Award Numbers:12104006,21873048,92056204National Research Foundation,Grant/Award Number:NRFNRFI2016-08Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20180319Start up fundations from Anhui UniversityTsinghua UniversityState Key Laboratory of Low-Dimensional Quantum Physics。
文摘Van der Waals heterojunctions are fast-emerging quantum structures fabricated by the controlled stacking of two-dimensional(2D)materials.Owing to the atomically thin thickness,their carrier properties are not only determined by the host material itself,but also defined by the interlayer interactions,including dielectric environment,charge trapping centers,and stacking angles.The abundant constituents without the limitation of lattice constant matching enable fascinating electrical,optical,and magnetic properties in van der Waals heterojunctions toward next-generation devices in photonics,optoelectronics,and information sciences.This review focuses on the charge and energy transfer processes and their dynamics in transition metal dichalcogenides(TMDCs),a family of quantum materials with strong excitonic effects and unique valley properties,and other related 2D materials such as graphene and hexagonalboron nitride.In the first part,we summarize the ultrafast charge transfer processes in van der Waals heterojunctions,including its experimental evidence and theoretical understanding,the interlayer excitons at the TMDC interfaces,and the hot carrier injection at the graphene/TMDCs interface.In the second part,the energy transfer,including both Förster and Dexter types,are reviewed from both experimental and theoretical perspectives.Finally,we highlight the typical charge and energy transfer applications in photodetectors and summarize the challenges and opportunities for future development in this field.
基金This work was financially supported by the National Natural Science Foundation of China(21788102 and 21673082)the National Basic Research Program of Chi-na(973 Program,2015CB655004)founded by MOST+2 种基金the Guangdong Natural Science Funds for Distinguished Young Scholar(2014A030306035)the Natural Science Foundation of Guangdong Province(2016A030312002)the Innovation and Technology Commission of Hong Kong(ITC-CNERC14SC01).
文摘Efficient electronic coupling is the key to constructing optoelectronic functionalπsystems.Generally,the delocalization ofπelectrons must comply with the framework constructed by covalent bonds(typicallyσbonds),representing classic through-bond conjuga-tion.However,through-space conjugation offers an alternative that achieves spatial electron communica-tionwith closely stacked π systems instead of covalent bonds thus enabling multidimensional energy and charge transport.