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hot-electron deposition and implosion mechanisms within electron shock ignition

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Chinese Physics B 2020年第10期29卷 354-362页

作者：尚万里车兴森孙奥杜华冰杨国洪韦敏习侯立飞杨轶濛张文海涂绍勇王峰何海恩杨家敏江少恩张保汉 Research Center of Laser Fusion China Academy of Engineering PhysicsMianyang 621900China

A hot-electron driven scheme can be more effective than a laser-driven scheme within suitable hot-electron energy and target density. In our one-dimensional (1D) radiation hydrodynamic simulations, 20× pressure enhancement was achieved when the ignitor laser spike was replaced with a 60-keV hot-electron spike in a shock ignition target designed for the National Ignition Facility (NIF), which can lead to greater shell velocity. Higher hot-spot pressure at the deceleration phase was obtained owing to the greater shell velocity. More cold shell material is ablated into the hot spot, and it benefits the increases of the hot-spot pressure. Higher gain and a wider ignition window can be observed in the hot-electron-driven shock ignition.

关键词： shock ignition inertial confinement fusion hot electron plasma fusion

hot electron generation on metal catalysts under surface reaction:Principles, devices, and application

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Chinese Chemical Letters 2018年第6期29卷 727-733页

作者： Ievgen I.Nedrygailov Hyosun Lee Si Woo Lee Jeong Young Park Center for Nanomaterials and Chemical Reactions Institute for Basic Science Graduate School of EEWS Korea Advanced Institute of Science and Technology(KAIST)

Understanding the fundamental mechanisms for charge transfer in supported catalysts is of great importance for heterogeneous catalysis. Several experimental and theoretical results suggest that charge flow through metal-support interfaces leads to the catalytic enhancement that is often observed in mixed catalysts. Therefore, it is crucial to directly probe this charge flow in metal-support catalysts during catalytic reactions. In this review, we consider the main aspects of research studying the processes that create and allow interfacial transfer of highly excited（hot） charge carriers in supported catalysts, and discuss the effect of this charge transfer on catalytic activity. We show a close connection between the phenomena of hot electron creation and chemical energy dissipation that accompanies catalytic reactions at both the gas/solid and liquid/solid interfaces. The intensity of hot electron flow is well correlated with the turnover rates of corresponding reactions, which opens up the possibility for developing new operando methodologies for studying chemical processes on catalytic surfaces.

关键词： hot electron Energy dissipation Heterogeneous catalysis Metal-support interactions Nanodiode

Ultra-high current gain tunneling hot-electron transfer amplifier based on vertical van der Waals heterojunctions

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Nano Research 2020年第8期13卷 2085-2090页

作者： Xu Zhao Peng Chen Xingqiang Liu Guoli Li Xuming Zou Yuan Liu Qilong Wu Yufang Liu Woo Jong Yu Lei Liao Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education&Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices School of Physics and ElectronicsChangsha410082China Henan Normal University School of PhysicsXinxiang453007China Department of electronic and Electrical Engineering Sungkyunkwan UniversitySuwon440-746Republic of Korea

Due to the backscattered parasitic current from the barriers,the current gain of the widely used amplifier is far from ideal.In this work,we demonstrate a vertical Au/Al2O3/BP/MoS2 tunneling hot-electron transfer amplifier with a hot-electron emitter-base junction and a p-n junction as the base-collector barrier.Fairly monoenergetic electrons traverse through the ultrathin Al2O3 dielectric via tunneling,which are accelerated and shifted to the collector region.The devices exhibit a high current on-off ratio of>105 and a high current density(JC)of∼1,000 A/cm2 at the same time.Notably,this work demonstrates a common-emitter current gain(β)value of 1,384 with a nanowatt power consumption at room temperature,which is a record high value among the all 2D based hot-electron transistors.Furthermore,the temperature dependent performance is investigated,and theβvalue of 1,613 is obtained at 150 K.Therefore,this work presents the potential of 2D based transistors for high-performance applications.

关键词： bipolar junction transistor hot electron van der Waals heterostructure current gain

Simulations of hot electron transport in radiation-ablated plasma

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Chinese Physics B 2023年第8期32卷 336-341页

作者：赵斌陶弢闫锐郑坚 Department of Mathematics and Physics Nanjing Institute of TechnologyNanjing 211167China IFSA Collaborative Innovation Center Shanghai Jiao Tong UniversityShanghai 200240China Department of Modern Mechanics University of Science and Technology of ChinaHefei 230026China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China

The transport of hot electrons in inertial confinement fusion(ICF)is integrated issue due to the coupling of hydrodynamic evolution and many physical processes.A hot electron transport code is developed and coupled with the radiation hydrodynamic code MULTI1D in this study.Using the code,the slowing-down process and ablation process of the hot electron beam are simulated.The ablation pressure scaling law of hot electron beam is confirmed in our simulations.The hot electron transport is simulated in the radiation-ablated plasmas relevant to indirect-drive ICF,where the spatial profile of hot electron energy deposition is presented around the shock compressed region.It is shown that the hot electron can prominently increase the total ablation pressure in the early phase of radiation-ablated plasma.So,our study suggests that a potential-driven symmetric mechanism may occur under the irradiation of asymmetric hot electron beam.The possible degradation from the hot electron transport and preheating is also discussed.

关键词： hot electron ablation indirect-drive ICF radiation-ablated plasmas

Thermal energy dependent transient permittivity of epsilon-near-zero material

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Science China(Physics,Mechanics & Astronomy) 2022年第8期65卷 96-101页

作者： Heng Wang Lixun Sun Kang Du Wending Zhang SooJin Chua Guixin Li Ting Mei MOE Key Laboratory of Material Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Optical Information TechnologySchool of Physical Science and TechnologyNorthwestern Polytechnical UniversityXi’an710129China Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen518055China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and TechnologyShenzhen518055China Department of Electrical and Computer Engineering National University of SingaporeSingapore117583Singapore LEES Program Singapore-MIT Alliance for Research&Technology(SMART)Singapore138602Singapore

Transparent conductive oxides exhibit attractive optical nonlinearity with ultrafast response and giant refractive index change near the epsilon-near-zero(ENZ) wavelength, originating from the intraband dynamics of conduction electrons. The optical nonlinearity of ENZ materials has been explained by using the overall-effective-mass and the overall-scattering-time of electrons in the extended Drude model. However, their response to optical excitation is yet the last building block to complete the theory. In this paper, the concept of thermal energy is theoretically proposed to account for the total energy of conduction electrons exceeding their thermal equilibrium value. The time-varying thermal energy is adopted to describe the transient optical response of indium-tin-oxide(ITO), a typical ENZ material. A spectrally-resolved femtosecond pump-probe experiment was conducted to verify our theory. By correlating the thermal energy with the pumping density, both the giant change and the transient response of the permittivity of ITO can be predicted. The results in this work provide a new methodology to describe the transient permittivities of ENZ materials, which will benefit the design of ENZ-based nonlinear photonic devices.

关键词： epsilon-near-zero optical nonlinearity transient response thermal energy hot electron indium tin oxide

Highly efficient electrocatalytic nitrogen fixation enabled by the bridging effect of Ru in plasmonic nanoparticles

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Nano Research 2023年第1期16卷 360-370页

作者： Hang Yin Jinwu Hu Caihong Fang Yuyang Wang Lixia Ma Nan Zhang Shouren Zhang Ruibin Jiang Jianfang Wang Shaanxi Key Laboratory for Advanced Energy Devices Shaanxi Engineering Lab for Advanced Energy TechnologySchool of Materials Science and EngineeringShaanxi Normal UniversityXi’an 710119China College of Chemistry and Materials Science The Key Laboratory of Functional Molecular SolidsMinistry of EducationAnhui Laboratory of Molecular-Based MaterialsCenter for Nano Science and TechnologyKey Laboratory of Electrochemical Clean Energy of Anhui Higher Education InstitutesAnhui Normal UniversityWuhu 241000China Henan Provincial Key Laboratory of Nanocomposites and Applications Institute of Nanostructured Functional MaterialsHuanghe Science and Technology CollegeZhengzhou 450006China Department of Physics The Chinese University of Hong KongHong Kong 999077China

Plasmon-generated hot electrons show great potential for driving chemical reactions.The utilization efficiency of hot electrons is highly dependent on the interaction of the electronic states at the interfaces between plasmonic nanoparticles and other materials/molecules.Strong interaction can produce new hybridized electron states,which permit direct hot-electron transfer,a more efficient transfer mechanism.However,Au usually has very weak interaction with most molecules because of its inertness,which makes direct hot-electron transfer impossible.Herein,the improvement of the hot-electron transfer efficiency from Au to N_(2)is demonstrated by introducing a Ru bridging layer.Both the N_(2)fixation rate and Faradic efficiency(FE)are enhanced by the excitation of plasmons.The enhancement of the N_(2)fixation rate is found to arise from plasmon-generated hot electrons.Theoretical calculations show that the strong interaction of the Ru electronic states with the N_(2)molecular orbitals produces new hybridized electronic states,and the Ru d electrons also strongly couple with the Au sp electrons.Such a bridging role of Ru makes direct hot-electron transfer from Au to N_(2)possible,improving the FE of nitrogen fixation.Our findings demonstrate a new approach to increasing the utilization efficiency of plasmonic hot electrons for chemical reactions and will be helpful to the design of plasmonic catalysts in the future.

关键词： electrocatalytic nitrogen fixation Au/Ru electrocatalysts localized surface plasmon resonance electronic state hybridization hot electron

Nanoplasmonic zirconium nitride photocatalyst for direct overall water splitting

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Chinese Chemical Letters 2022年第3期33卷 1271-1274页

作者： Yu Liu Xiaowei Zhang Lisha Lu Jun Ye Jianlin Wang Xiaomin Li Xuedong Bai Wenlong Wang Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesChinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

The ability of plasmonic nanostructures to efficiently harvest light energy and generate energetic hot carriers makes them promising materials for utilization in photocatalytic water spitting. Apart from the traditional Au and Ag based plasmonic photocatalysts, more recently the noble-metal-free alternative plasmonic materials have attracted ever-increasing interest. Here we report the first use of plasmonic zirconium nitride (ZrN) nanoparticles as a promising photocatalyst for water splitting. Highly crystalline ZrN nanoparticles with sizes dominating at 30-50 nm were synthesized that exhibit intense visible and near-infrared absorption due to localized surface plasmon resonance (LSPR). Without utilizing any noble metal cocatalysts such as Pt, the plasmonic ZrN nanoparticles alone showed stable photocatalytic activity for H_(2) evolution in aqueous solution with methanol as sacrificial electron donor. The addition of a cobalt oxide (CoO_(x)) cocatalyst can facilitate the separation of photogenerated charge carriers and further improve the photocatalytic activity. The optimized CoO_(x) modified ZrN photocatalyst was observed not only to activate the O_(2) evolution reaction with presence of electron acceptor, but also to drive overall water splitting for the simultaneous H_(2) and O_(2) evolution in the absence of any sacrificial agents.

关键词： Zirconium nitride Surface plasmon Noble–metal–free Photocatalytic water splitting hot electron

Quantifying plasmon resonance and interband transition contributions in photocatalysis of gold nanoparticle

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Chinese Physics B 2021年第7期30卷 456-460页

作者：董亮张成云严蕾张宝宝陈环弥小虎付正坤张正龙郑海荣 School of Physics and Information Technology Shaanxi Normal UniversityXi'an 710062China

Localized surface plasmon has been extensively studied and used for the photocatalysis of various chemical reactions.However,the different contributions between plasmon resonance and interband transition in photocatalysis has not been well understood.Here,we study the photothermal and hot electrons effects for crystal transformation by combining controlled experiments with numerical simulations.By photo-excitation of Na YF4:Eu^(3+)@Au composite structure,it is found that the plasmonic catalysis is much superior to that of interband transition in the experiments,owing to the hot electrons generated by plasmon decay more energetic to facilitate the reaction.We emphasize that the energy level of hot electrons plays an essential role for improving the photocatalytic activity.The results provide guidelines for improving the efficiency of plasmonic catalysis in future experimental design.

关键词： surface plasmon interband transition hot electron photothermal effect

Broadband terahertz radiation from a biased two-dimensional electron gas in an AlGaN/GaN heterostructure

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Journal of Semiconductors 2015年第10期36卷 55-59页

作者：郑中信孙建东周宇张志鹏秦华 Key Laboratory of Nanodevices and Applications Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of Sciences University of Chinese Academy of Sciences

The broadband terahertz （THz） emission from drifting two-dimensional electron gas （2DEG） in an AI- GaN/GaN heterostructure at 6 K is reported. The devices are designed as THz plasmon emitters according to the Smith-Purcell effect and the ＇shallow water＇ plasma instability mechanism in 2DEG. Plasmon excitation is excluded since no signature of electron-density dependent plasmon mode is observed. Instead, the observed THz emission is found to come from the heated lattice and/or the hot electrons. Simulated emission spectra of hot electrons taking into account the THz absorption in air and Fabry-Pérot interference agree well with the experiment. It is confirmed that a blackbody-like THz emission will inevitably be encountered in similar devices driven by a strong in-plane electric field. A conclusion is drawn that a more elaborate device design is required to achieve efficient plasmon excitation and THz emission.

关键词： two-dimensional electron gas hot electron blackbody radiation plasmon Fabry-Pérot cavity