（2＋1）-Dimensional Electron Acoustic Solitary Waves in an Unmagnetized Collisionless Plasma with Vortex-Like Hot Electrons

In this paper, （2＋1）-dimensional electron acoustic waves （EAW） in an unmagnetized collisionless plasma have been studied by the linearized method and the reductive perturbation technique, respectively. The dispersion relation and a modified Kadomtsev-Petviashvili （KP） equation have been obtained for the EAW in the plasma considering a cold electron fluid and a vortex-like hot electrons. It is found from some numerical results that the parameter β（the ratio of the free hot electron temperature to the hot trapped electron temperature） effects on the amplitude and the Width of the electron acoustic solitary waves （EASW）. It can be indicated that the free hot electron temperature and the hot trapped electron temperature have very important effect on the characters of the propagation for the EASW.

Effects of atomic number Z on the energy distribution of hot electrons generated by femtosecond laser interaction with metallic targets

The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and 7×10^17W/cm^2 laser pulses with metallic targets have been studied experimentally. The results show that the number and the effective temperature of hot electrons increase with the atomic number Z of metallic targets, and the temperature of hot electrons are in the range of 190-230keV, which is consistent with a scaling law of hot electrons temperature.

Impact of substrate injected hot electrons on hot carrier degradation in a 180-nm NMOSFET

Although hot carriers induced degradation of NMOSFETs has been studied for decades, the role of hot electron in this process is still debated. In this paper, the additional substrate hot electrons have been intentionally injected into the oxide layer to analyze tile role of hot electron in hot carrier degradation. The enhanced degradation and the decreased time exponent appear with the injected hot electrons increasing, the degradation increases from 21.80% to 62.00% and the time exponent decreases from 0.59 to 0.27 with Vb decreasing from 0 V to -4 V, at the same time, the recovery also becomes remarkable and which strongly depends on the post stress gate bias Vg. Based on the experimental results, more unrecovered interface traps are created by the additional injected hot electron from the breaking Si-H bond, but the oxide trapped negative charges do not increase after a rapid recovery.

Hot electrons in water: injection and ponderomotive acceleration by means of plasmonic nanoelectrodes

We present a theoretical and experimental study of a plasmonic nanoelectrode architecture that is able to inject bunches of hot electrons into an aqueous environment.In this approach,electrons are accelerated in water by ponderomotive forces up to energies capable of exciting or ionizing water molecules.This ability is enabled by the nanoelectrode structure(extruding out of a metal baseplate),which allows for the production of an intense plasmonic hot spot at the apex of the structure while maintaining the electrical connection to a virtually unlimited charge reservoir.The electron injection is experimentally monitored by recording the current transmitted through the water medium,whereas the electron acceleration is confirmed by observation of the bubble generation for a laser power exceeding a proper threshold.An understanding of the complex physics involved is obtained via a numerical approach that explicitly models the electromagnetic hot spot generation,electron-by-electron injection via multiphoton absorption,acceleration by ponderomotive forces and electron-water interaction through random elastic and inelastic scattering.The model predicts a critical electron density for bubble nucleation that nicely matches the experimental findings and reveals that the efficiency of energy transfer from the plasmonic hot spot to the free electron cloud is much more efficient(17 times higher)in water than in a vacuum.Because of their high kinetic energy and large reduction potential,these proposed wet hot electrons may provide new opportunities in photocatalysis,electrochemical processes and hot-electron driven chemistry.

High activity of hot electrons from bulk 3D graphene materials for efficient photocatalytic hydrogen production

Design and synthesis of efficient photocatalysts for hydrogen production via water splitting are of great importance from both theoretical and practical viewpoints. Many metal-based semiconductors have been explored for this purpose in recent decades. Here, for the first time, an entirely carbon-based material, bulk three-dimensionally cross-linked graphene （3DG）, has been developed as a photocatalyst for hydrogen production. It exhibits a remarkable hydrogen production rate of 270 μmol-h-l.g-t under full-spectrum light via a hot/free electron emission mechanism. Furthermore, when combined with the widely used semiconductor TiO2 to form a TiO2/3DG composite, it appears to become a more efficient hydrogen production photocatalyst. The composite achieves a production rate of 1,205 bimol-h μg-t under ultraviolet-visible （UV-vis） light and a 7.2% apparent quantum efficiency at 350 nm due to the strong synergetic effects between TiO2 and 3DG.

Simulations of hot electron transport in radiation-ablated plasma

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.

Hot electron electrochemistry at silver activated by femtosecond laser pulses

A silver microelectrode with a diameter of 30μm in an aqueous K_(2)SO_(4) electrolyte was irradiated with 55 fs and 213 fs laser pulses.This caused the emission of electrons which transiently charged the electrochemical double layer.The two applied pulse durations were significantly shorter than the electron-phonon relaxation time.The laser pulse durations had negligible impact on the emitted charge,which is incompatible with multiphoton emission.On the other hand,the ob-served dependence of emitted charge on laser fluence and electrode potential supports the thermionic emission mechanism.

Photocatalytic N2 Fixation by Plasmonic Mo-Doped TiO_(2) Semiconductor

Photocatalytic N_(2)xation has attracted substantial attention in recent years,as it represents a green and sustainable devel-opment route toward effciently convert-ing N_(2)to NH_(3)for industrial applications.How to rationally design catalysts in this regard remains a challenge.Here we pro-pose a strategy that uses plasmonic hot electrons in the highly doped TiO_(2)to ac-tivate the inert N_(2)molecules.The synthesized semiconductor catalyst Mo-doped TiO_(2)shows a NH_(3)production effciency as high as 134μmol·g^(-1)·h^(-1)under ambient conditions,which is comparable to that achieved by the conventional plasmonic gold metal.By means of ultra-fast spectroscopy we reveal that the plasmonic hot electrons in the system are responsible for the activation of N_(2)molecules,enabling improvement the catalytic activity of TiO_(2).This work opens a new avenue toward semiconductor plasmon-based photocatalytic N_(2)xation.

A Novel Flash Memory Using Band-to-Band Tunneling Induced Hot Electron Injection to Program

A novel band to band hot electron programming flash memory device,which features programming with high speed,low voltage,low power consumption,large read current and short access time,is proposed.The new memory cell is programmed by band to band tunneling induced hot electron (BBHE) injection method at the drain,and erased by Fowler Nordheim tunneling through the source region.The work shows that the programming control gate voltage can be reduced to 8V,and the drain leakage current is only 3μA/μm.Under the proposed operating conditions,the program efficiency and the read current rise up to 4×10 -4 and 60μA/μm,respectively,and the program time can be as short as 16μs

Gold/monolayer graphitic carbon nitride plasmonic photocatalyst for ultrafast electron transfer in solar-to-hydrogen energy conversion

Gold(Au)plasmonic nanoparticles were grown evenly on monolayer graphitic carbon nitride(g‐C3N4)nanosheets via a facile oil‐bath method.The photocatalytic activity of the Au/monolayer g‐C3N4 composites under visible light was evaluated by photocatalytic hydrogen evolution and environmental treatment.All of the Au/monolayer g‐C3N4 composites showed better photocatalytic performance than that of monolayer g‐C3N4 and the 1%Au/monolayer g‐C3N4 composite displayed the highest photocatalytic hydrogen evolution rate of the samples.The remarkable photocatalytic activity was attributed largely to the successful introduction of Au plasmonic nanoparticles,which led to the surface plasmon resonance(SPR)effect.The SPR effect enhanced the efficiency of light harvesting and induced an efficient hot electron transfer process.The hot electrons were injected from the Au plasmonic nanoparticles into the conduction band of monolayer g‐C3N4.Thus,the Au/monolayer g‐C3N4 composites possessed higher migration and separation efficiencies and lower recombination probability of photogenerated electron‐hole pairs than those of monolayer g‐C3N4.A photocatalytic mechanism for the composites was also proposed.

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

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.

Hot-electron deposition and implosion mechanisms within electron shock ignition

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.

Noise temperature distribution of superconducting hot electron bolometer mixers

We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer(DATE5)telescope.By evaluating the double sideband(DSB)receiver noise temperature(Trec)across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points,a broad optimal bias region has been observed,illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point.The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components,whose transmissions have been measured by a time-domain spectroscopy.The corrected noise temperature distribution shows a frequency independence relation.The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated,the bath temperature has limited effect on the lowest receiver noise temperature until 7 K,however the optimal bias region deteriorates obviously with increasing bath temperature.

Terahertz Direct Detectors Based on Superconducting Hot Electron Bolometers with Microwave Biasing

Terahertz （THz） direct detectors based on superconducting niobium nitride （NbN） hot electron bolometers （HEBs） with microwave （MW） biasing are studied. The MW is used to bias the HEB to the optimum point and to readout the impedance changes caused by the incident THz signals. Compared with the thermal biasing method, this method would be more promising in large scale array with simple readout. The used NbN HEB has an excellent performance as heterodyne detector with the double sideband noise temperature （T N） of 403K working at 4.2K and 0.65THz. As a result, the noise equivalent power of 1.5pW/Hz 1/2 and the response time of 64ps are obtained for the direct detectors based on the NbN HEBs and working at 4.2K and 0.65THz.

In situ photoelectric biosensing based on ultranarrowband near-infrared plasmonic hot electron photodetection

Narrowband photodetection is an important measurement technique for material analysis and sensing,for example,nondispersive infrared sensing technique.Both photoactive material engineering and nanophotonic filtering schemes have been explored to realize wavelength-selective photodetection,while most devices have a responsive bandwidth larger than 2%of the operating wavelength,limiting sensing performance.Near-infrared photodetection with a bandwidth of less than 0.2%of the operating wavelength was demonstrated experimentally in Au/Si Schottky nanojunctions.A minimum linewidth of photoelectric response down to 2.6 nm was obtained at a wavelength of 1550 nm by carefully tailing the absorptive and radiative loss in the nanostructures.Multiple functions were achieved on chip with the corrugated Au film,including narrowband resonance,light harvesting for sensing and photodetection,and electrodes for hot electron emission.Benefiting from such a unity integration with in situ photoelectric conversion of the optical sensing signal and the ultranarrowband resonance,self-contained on-chip biosensing via simple intensity interrogation was demonstrated with a limit of detection down to 0.0047%in concentration for glucose solution and 150 ng∕m L for rabbit IgG.Promising potential of this technique is expected for the applications in on-site sensing,spectroscopy,spectral imaging,etc.

On-Resistance Degradations Under Different Stress Conditions in High Voltage pLEDMOS Transistors and an Improved Method

The on-resistance degradations of the p-type lateral extended drain MOS transistor （pLEDMOS） with thick gate oxide under different hot carrier stress conditions are different, which has been experimentally investigated. This difference results from the interface trap generation and the hot electron injection, and trapping into the thick gate oxide and field oxide of the pLEDMOS transistor. An improved method to reduce the on-resistance degradations is also presented, which uses the field oxide as the gate oxide instead of the thick gate oxide. The effects are analyzed with a MEDICI simulator.

Kink effect in current–voltage characteristics of a GaN-based high electron mobility transistor with an AlGaN back barrier

The kink effect in current-voltage （IV） characteristic s seriously deteriorates the performance of a GaN-based HEMT. Based on a series of direct current （DC） IV measurements in a GaN-based HEMT with an AlGaN back barrier, a possible mechanism with electron-trapping and detrapping processes is proposed. Kink-related deep levels are activated by a high drain source voltage （Vds） and located in a GaN channel layer. Both electron trapping and detrapping processes are accomplished with the help of hot electrons from the channel by impact ionization. Moreover, the mechanism is verified by two other DC IV measurements and a model with an expression of the kink current.

Near-field and photocatalytic properties of mono-and bimetallic nanostructures monitored by nanocavity surface-enhanced Raman scattering

Localized surface plasmon resonances(LSPR)generated in a particle-film nanocavity enhance electric fields within a nanoscale volume.LSPR can also decay into hot carriers,highly energetic species that catalyze photocatalytic reactions in molecular analytes located in close proximity to metal surfaces.In this study,we examined the intensity of the electric field(near-field)and photocatalytic properties of plasmonic nanocavities formed by single nanoparticles(SNP)on single nanoplates(SNL).Using 4-nitrobenzenethiol(4-NBT)as a molecular reporter,we determined the near-field responses,as well as measured rates of 4-NBT dimerization into 4,4-dimercaptoazobenzene(DMAB)in the gold(Au)SNP on AuSNL nanocavity(Au-Au),as well as in AuSNP on AgSNL(Au-Ag),AgSNP on AuSNL(Ag-Au),and AgSNP on AgSNL(Ag-Ag)nanocavities using 532,660,and 785 nm excitations.We observed the strongest near-field signals of 4-NBT at 660 nm in all examined plasmonic systems that is found to be substantially red-shifted relative to the LSPR of the corresponding nanoparticles.We also found that rates of DMAB formation were significantly greater in heterometal nanocavities(Au-Ag and Ag-Au)compared to their monometallic counterparts(Au-Au and Ag-Ag).These results point to drastic differences in plasmonic and photocatalytic properties of mono and bimetallic nanostructures.

Recent Progress in Chiral Absorptive Metamaterials

Chiral metamaterial absorbers(CMMAs),a particular class of chiral metamaterials that refuse the transmission of incident radiation and exhibit different optical responses upon interactions with left and right circularly polarized(RCP)light,have gained research traction in recent years.CMMAs demonstrate numerous exotic and specialized applications owing to their achievable compatibility with various physical,chemical,and biomolecular systems.Aside from their well-evolved fabrication modalities for a broad range of frequencies,CMMAs exhibit strong chiroptical effects,making them central to various detection,imaging,and energy harvesting applications.Consequently,within the past decade,studies encompassing the design,optimization,and fabrication,as well as demonstrating the diverse applications of CMMAs have emerged.In this review,the theory,design,and fabrication of CMMAs are discussed,highlighting their top-down fabrication techniques as well as recent algorithmic and machine-learning(ML)-based approaches to the design and optimization.Some of their broad-spectrum applications are also discussed,spanning their roles in enantioselective photodetection,chiral imaging,generation of hot electrons,selective temperature sensing,and active chiral plasmonics.

Recent review of surface plasmons and plasmonic hot electron effects in metallic nanostructures

Plasmonic resonators are widely used for the manipulation of light on subwavelength scales through the near-field electromagnetic wave produced by the collective oscillation of free electrons within metallic systems,well known as the surface plasmon(SP).The non-radiative decay of the surface plasmon can excite a plasmonic hot electron.This review article systematically describes the excitation progress and basic properities of SPs and plasmonic hot electrons according to recent publications.The extraction mechanism of plasmonic hot electrons via Schottky conjunction to an adjacent semiconductor is also illustrated.Also,a calculation model of hot electron density is given,where the efficiency of hot-electron excitation,transport and extraction is discussed.We believe that plasmonic hot electrons have a huge potential in the future development of optoelectronic systems and devices.