Role Of Hot Electrons Research Articles

Synergistic effect of NiO-loaded gold NPs modified exfoliated graphitic carbon nitride (E-gC3N4) with the role of hot electrons and hole scavengers for boosting solar hydrogen production

The photocatalytic hydrogen production capabilities of a well-designed NiO–Au loaded exfoliated graphitic carbon nitride (E-gC3N4) were evaluated after it was synthesized in a straightforward, template-free, single-step process. This study delves into the synergistic impact of utilizing exfoliated g-C3N4 (E-gC3N4) loaded with NiO to trap electrons and plasmonic Au to elevate solar-driven H2 evolution through the surface plasmon resonance effect. Using 2 % NiO/E-gC3N4 and 0.3 % Au/E-gC3N4 samples, the H2 yield of 2620 and 2725 μmol g−1, were obtained, which were 25 and 26 folds higher than using bulk g-C3N4, respectively. The highest photocatalytic H2 production of 4750 μmol g−1 was obtained with 1 % NiO-0.3 % Au/E-gC3N4, which was 1.74, 1.81 and 45.24-fold more than it was produced with 0.3 % Au/E-gC3N4, 2 % NiO/E-gC3N4 and bulk g-C3N4 samples, respectively. Increased visible light absorption and charge production due to the SPR effect of Au and efficient charge separation due to NiO co-catalyst led to an increase in H2 generation. The composite was also stable for the consecutive four cycles, in which continuous H2 evolution was obtained. This novel strategy offers promise for synthesizing effective composites for visible-light-driven H2 evolution.

Role of hot electrons in mitigating ablative Rayleigh–Taylor instability

In laser-driven inertial confinement fusion (ICF) specifically with high laser intensities, energetic (hot) electrons (HEs) can be generated via laser-plasma instabilities. HEs can significantly impact the target performance by modifying the implosion hydrodynamics. In this paper, the effects of moderate-energy (about 20 to 40 keV) HEs on the evolution of two-dimensional single-mode ablative Rayleigh–Taylor instability (ARTI) are studied through numerical simulations with a multigroup diffusion model in which the HE population is treated as a high-energy group launched from the boundary. With HEs present, it is found that ARTI linear growth rates are reduced even though the acceleration of the implosion shell is enhanced by HEs. The reduction in the linear growth rate is owing to the increase in the ablation velocity and the density scale length, and this stabilization effect is greater in the shorter-wavelength modes and/or higher-energy HE cases. The ARTI linear growth does not get mitigated monotonically as the HE number density increases for a given fixed HE kinetic energy. The HE number density minimizing the ARTI growth rate is found, likely due to the competition of the stabilizing and destabilizing hydrodynamic-parameter variations caused by HEs.

Synergistic effect of gold NPs modified graphitic carbon nitride nanotubes (g-CNT) with the role of hot electrons and hole scavengers for boosting solar hydrogen production

The efficient and selective photocatalysts for the evolution of hydrogen are highly demanding, however, many semiconductors are complex in nature and have lower photocatalytic efficiency. This is because of their small exposed surface area, poor light penetration, and unregulated charge recombination rate. Herein, well-designed graphitic carbon nitride with hierarchical nanotextures loaded with plasmonic gold (Au) nanoparticles has been investigated for stimulating photocatalytic H2 evolution. Hole scavengers, diffusion effects, duration, and mass transfer were used to evaluate the photoactivity activity in a slurry type continuous flow photoreactor system. Due to better charge carrier separation and enhanced light permeability, H2 evolution was boosted by two times when bulk g-C3N4 structure was alternated with graphitic carbon nitride nanotubes (g-CNT). The maximum H2 generation rate was 455 μmol g−1 h−1 with 0.3% Au/g-CNT nanotexture, which was 17.8 and 8.9 times greater than utilizing g-C3N4 and g-CNT samples, respectively. The key factors influencing this improvement in photoactivity were the unique interlayer opening, higher light penetration, more light utilization due to plasmonic effect, enhanced surface reactive active sites, and decreased charge carrier recombination. The hot electrons due to plasmonic gold was another important feature to promote H2 evolution rate under solar energy. It is possible to employ these freshly developed nanotextures, which have a gold plasmonic effect, for solar energy conversion and other energy-related applications.

Role of hot electrons in shock ignition constrained by experiment at the National Ignition Facility

Shock ignition is a scheme for direct drive inertial confinement fusion that offers the potential for high gain with the current generation of laser facility; however, the benefits are thought to be dependent on the use of low adiabat implosions without laser–plasma instabilities reducing drive and generating hot electrons. A National Ignition Facility direct drive solid target experiment was used to calibrate a 3D Monte Carlo hot-electron model for 2D radiation-hydrodynamic simulations of a shock ignition implosion. The α=2.5 adiabat implosion was calculated to suffer a 35% peak areal density decrease when the hot electron population with temperature Th=55 keV and energy Eh=13 kJ was added to the simulation. Optimizing the pulse shape can recover ∼1/3 of the peak areal density lost due to a change in shock timing. Despite the harmful impact of laser–plasma instabilities, the simulations indicate shock ignition as a viable method to improve performance and broaden the design space of near ignition high adiabat implosions.

Experimental study of charging of dust grains in the presence of energetic electrons

The role of hot electrons in the charging of dust grains is investigated in a two temperature hydrogen plasma. A variety of dust particles are introduced into the system and secondary electron emission (SEE) from each of the dust types has been reported. A cylindrical Langmuir probe is used for determining the plasma parameters and a Faraday cup is connected to an electrometer in order to measure the dust current. The electrometer readings confirm the electron emission from the dust and SEE is observed from the tungsten dust in a low-pressure experimental plasma device for the first time.

The role of hot electrons on ultrahigh pressure generation relevant to shock ignition conditions

On shock ignition (SI) scheme of inertial confinement fusion (ICF), a spherical shell target is compressed by relatively low intensity laser pulse irradiation, and hot spot is ignited by converging shock waves by high intensity laser pulse called “spike pulse”. The SI scheme is considered as a promising scheme to reduce the required drive laser energy for ignition. On the SI scheme, the strong shock by the spike pulse should be over 300 Mbar (=30 TPa). The key physics to produce such ultrahigh pressure is the contribution of hot electrons generated by parametric instabilities. The hot electron generation, transport, and their effects on shock wave parameters in various experimental conditions were explored. This paper focuses on experimental parameter of 0.527 μm (2ω) irradiation as spike pulse with/without pre-pulse irradiation conditions, and the experimental data was compared with one-dimensional hydrodynamic simulation. Experiments with pre-pulse irradiation that pre-compresses a target before the main pulse with producing more hot electrons generates a strong shock and hot electrons lead to an enhanced shock velocity. This fact indicates that the hot electron absorption per unit length in the target is increased leading to an enhanced shock strength.

Role of Hot Electrons in the Development of GaAs‐Based Spin Hall Devices with Low Power Consumption

Strong inverse spin Hall effect (ISHE) signal can be realized in GaAs via the electrical injection of hot electrons. In a recent article, it was demonstrated that optically induced hot electrons can also lead to the establishment of ISHE in GaAs but at much lower electric field. Herein, the combined role of high electric field and high energy optical injection of hot electrons in GaAs is examined. An anomalous behavior of ISHE voltage (VISHE) is observed. Spin‐polarized hot‐electrons are optically injected in the conduction band of n‐GaAs which are then transferred from Γ to L valley with or without applied bias. At 2.33 eV excitation energy (Eex), a monotonous increase in VISHE is seen with electric field which starts to fall beyond a critical electric field. A theoretical framework based on the rate equations governing intervalley scattering is proposed, which successfully explains the observed behavior. Utilizing optically injected hot electrons at Eex = 2.33 eV, a spin Hall device is demonstrated, that consumes less power and yields better signal‐to‐noise ratio. These findings are highly encouraging for the development of next‐generation spin‐optoelectronic devices.

The role of hot electrons in the dynamics of a laser-driven strong converging shock

Experiments on strong shock excitation in spherical plastic targets conducted at the Omega Laser Facility are interpreted with the radiation–hydrodynamics code CHIC to account for parametric instabilities excitation and hot-electron generation. The effects of hot electrons on the shock-pressure amplification and upstream preheat are analyzed. It is demonstrated that both effects contribute to an increase in the shock velocity. Comparison of the measured laser reflectivity and shock flash time with numerical simulations makes it possible to reconstitute the time history of the ablation and shock pressures. Consequences of this analysis for the shock-ignition target design are discussed.

Roles of hot electrons in generating upper-hybrid waves in the earth's radiation belt

Electrostatic fluctuations near upper-hybrid frequency, which are sometimes accompanied by multiple-harmonic electron cyclotron frequency bands above and below the upper-hybrid frequency, are common occurrences in the Earth's radiation belt, as revealed through the twin Van Allen Probe spacecrafts. It is customary to use the upper-hybrid emissions for estimating the background electron density, which in turn can be used to determine the plasmapause locations, but the role of hot electrons in generating such fluctuations has not been discussed in detail. The present paper carries out detailed analyses of data from the Waves instrument, which is part of the Electric and Magnetic Field Instrument Suite and Integrated Science suite onboard the Van Allen Probes. Combined with the theoretical calculation, it is shown that the peak intensity associated with the upper-hybrid fluctuations might be predominantly determined by tenuous but hot electrons and that denser cold background electrons do not seem to contribute much to the peak intensity. This finding shows that upper-hybrid fluctuations detected during quiet time are not only useful for the determination of the background cold electron density but also contain information on the ambient hot electrons population as well.

ChemInform Abstract: Role of Hot Electrons and Metal‐Oxide Interfaces in Surface Chemistry and Catalytic Reactions

AbstractReview: 264 refs.

Role of hot electrons and metal-oxide interfaces in surface chemistry and catalytic reactions.

ADVERTISEMENT RETURN TO ISSUEReviewNEXTRole of Hot Electrons and Metal–Oxide Interfaces in Surface Chemistry and Catalytic ReactionsJeong Young Park*†‡, L. Robert Baker§, and Gabor A. Somorjai*∥⊥View Author Information† Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea‡ Graduate School of EEWS, KAIST, Daejeon 305-701, South Korea§ Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States∥ Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States⊥ Materials Sciences and Chemical Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, California 94720, United States*E-mail: [email protected]*E-mail: [email protected]Cite this: Chem. Rev. 2015, 115, 8, 2781–2817Publication Date (Web):March 20, 2015Publication History Received6 June 2013Published online20 March 2015Published inissue 22 April 2015https://doi.org/10.1021/cr400311pCopyright © 2015 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views8687Altmetric-Citations235LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (13 MB) Get e-AlertsSUBJECTS:Catalysts,Hot electrons,Metals,Oxides,Platinum Get e-Alerts

Conversion efficiency and spectral broadening of the K-α line emitted from planar titanium targets irradiated with ultra-short laser pulses of high intensity

A study of the conversion efficiency and line shape of the K-α x-ray line radiation from a planar titanium target irradiated by an ultra-short laser pulse is performed. The conversion efficiency and spectral broadening are studied as a function of laser intensity (5 × 1016–1018 W cm−2), laser pulse duration (45 fs–800 fs), and laser fluence (2 × 103–4.2 × 104 J cm−2). The K-α1 line (4510 eV) is observed to be broadened (up to ∼9 eV), predominantly towards the higher energy side and strongly depends on the laser fluence rather than on laser intensity. The reason for the spectral broadening is attributed to K-α emission in warm dense plasma. The role of hot electrons and direct laser heating on spectral broadening is outlined. In addition to this, our observations indicates that the presence of pre-plasma strongly contribute to the observed broadening through the inner-shell transitions in multiply charged titanium ions in the pre-plasma. The appropriate laser irradiation parameters to achieve high conversion efficiency and minimum spectral width of the K-α radiation are identified. The study is important, since the control of the spectral profile is of general interest for diffraction or scattering experiments in view of its potential in increasing temporal resolution.

Size effect on thermal desorption of CO from Pt nanostructures on graphite

Self-assembled Pt nanostructures, which are formed by evaporation and subsequent diffusion limited aggregation of Pt on graphite, have been studied by photoemission and scanning electron microscopy. Adsorption of CO has been studied by temperature programmed desorption. Charge induced Pt 4f core level shifts in the order of 1 eV that depend on the effective dimensions of the nanostructures have been observed, and effective dimensions of the Pt structures have been defined based on the Pt 4f core level shifts. The effective dimensions of the Pt structures have been correlated with changes in the thermal desorption of adsorbed CO. It is observed that smaller effective dimensions in the few nanometer range result in lower desorption temperatures of up to 50 K. The possible role of hot electrons in the adsorption process has been discussed.

Electron induced dissociation of hydrogen or deuterium–silicon complexes in GaAs; application to the reliability of GaAs based electronic or optoelectronic devices

The results obtained, very recently, in n-type Si-doped GaAs passivated with a hydrogen (H) or deuterium (D) plasma, on the stability of the Si–H or Si–D complexes are summarized. It is shown that a strong dissociation of the Si–H or Si–D complexes, associated with a large isotope effect is observed when hot electrons are produced or externally injected (using an electron-beam) in Si-doped hydrogenated or deuterated GaAs. The application of these results to the reliability of III–V devices is studied. The role of hot electrons is described and the device lifetime improvement, which could be obtained by using suitable thermal annealings, is discussed.

Isotope effect on the reactivation of neutralized Si dopants in hydrogenated or deuterated GaAs: The role of hot electrons

Room-temperature bias stress and annealing experiments have been performed on hydrogenated and deuterated Si doped n-type GaAs Schottky diodes. From a careful analysis of capacitance–voltage characteristics, we have studied the variation of the active doping concentration and the reactivation of neutralized dopants. In thermal annealing experiments at 250 °C, the Si–H complex dissociation rate does not vary significantly by incorporating deuterium rather than hydrogen. On the contrary, by applying high reverse bias voltages to the Schottky diodes at room temperature, a strong isotope effect is observed on the dissociation rate. In this case, the dopant reactivation should be due to hot electron excitations.

Investigation of the role of hot holes and hot electrons in the generation of interface states in submicrometre MOSFETs using a new charge-profiling technique based on charge-pumping measurements

The roles of hot electrons and hot holes in the generation of interface states in MOSFETs have been a controversial issue, due to the different interpretations of experimental data. In this article, a new physics-based charge-extraction algorithm, based on charge-pumping measurements, is used to investigate the roles of electrons and holes in the generation of interface states in submicrometre p-channel and n-channel MOSFETs. Our results show that while hot holes play an important role in the creation of interface states in submicrometre nMOSFETs, hot electrons are the main contributors to the interface-state generation in submicrometre buried-channel pMOSFETs. Therefore different analysis is required when characterizing the hot-carrier behaviour of pMOSFETs and nMOSFETs.