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Experimental Evaluation and Analysis of Switching Transient's Effect on Dynamic On-Resistance in GaN HEMTs
摘要： The dynamic on-resistance is problematic as it can impair the converter's efficiency due to the increased conduction loss. In this paper, the hard-switching transient's effect on the dynamic on-resistance is, for the first time, evaluated experimentally on a commercial high-voltage GaN HEMT. A new R_dyn-ds,on measurement circuit with fast sensing speed is designed, and an accurate measurement of R_dyn-ds,on can be realized experimentally within 49.6 ns after the device's current reaches to the load current. A double-pulse-test setup is designed to comprehensively evaluate the switching transient's effect on R_dyn-ds,on under different operating conditions. From the experimental results, it is found that the turn-on and turn-off gate resistance have a significant impact on the dynamic on-resistance whereas the cross-talk effect on R_dyn-ds,on is negligible. Specifically, at 400 V/25 A, more than 27% (28.2%) increase in R_dyn-ds,on is observed when the external turn-on (turn-off) gate resistance increases from 0 Ω to 20 Ω. Detailed discussion and quantitative analysis are provided to explain the experimental results. In terms of the turn-on process, it is concluded that the R_dyn-ds,on variation is mainly caused by the different numbers of generated hot electrons. For the turn-off transient, it is confirmed the variation of drain current at different dv/dt slew rate leads to the R_dyn-ds,on difference.
关键词： switching transients,Dynamic on-resistance,GaN HEMTs,hot electrons
更新于2025-09-23 15:22:29
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Mechanism of Liquid-Phase Reductive Thin-Film Deposition under Quasiballistic Electron Incidence
摘要： Highly reducing activity of quasiballistic hot electrons emitted from a nanocrystalline silicon (nc-Si) diode is veri?ed in terms of liquid-phase thin ?lm deposition. Incident electrons reduce positive ions in salt solutions coated on a target substrate, and then result in deposition of thin metal (Cu) and semiconducting (Si, Ge, and SiGe) ?lms. This mechanism is investigated here throughout the process from electron incidence to thin ?lm deposition. Thermodynamic criterion deduced from classical nucleation theory suggests that the output electron energy of the nc-Si emitter is suitable for promoting preferential reduction of target ions in solutions leading to the nuclei formation. In accordance with mass-transport analyses on generated nanoclusters, the most primary factor of thin ?lm growth is the dose of incident electron. The formulated deposition rate rapidly increases and reaches a stationary value within 0.1 s after electron incidence. The theoretical dependency of the thin ?lm thickness on the electron incidence time is consistent with the experimental results. Speci?c features of this scheme as an alternative approach for thin ?lm deposition are discussed in comparison with the conventional dry and wet processes.
关键词： nanocrystalline silicon diode,quasiballistic hot electrons,mass-transport analyses,thermodynamic criterion,liquid-phase thin film deposition
更新于2025-09-23 15:21:21
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Effects of continuous phase plate on plasma corona homogeneity and laser-plasma instabilities in experiments with three target materials
摘要： Corona homogeneity and spectra of scattered light and hot electrons produced by laser-plasma instabilities inside laser-produced plastic, aluminum, and gold plasmas were investigated with and without the use of continuous phase plate (CPP) to the laser beam. Improvement of the corona homogeneity was observed for all three materials after applying CPP, while the inhibition of the intensity of backward-scattered light and the amount of emitted hot electrons was not always synchronous for different materials, which is interpreted as a result of the changes in thresholds of the stimulated Raman scattering (SRS) and the two-plasmon decay (TPD) instability before and after the application of CPP. By comparing the changes of SRS scattered light intensity with the amount of hot electrons in different kinetic energy ranges for all three target materials in our experiments, we conclude that SRS is more responsible for the diagnosed hot electrons between 50–150 keV, and those above 150 keV should be generated by TPD, which could be explained by the difference in phase velocity of electron plasma waves between SRS and TPD calculated from measured and simulated parameters of corona and laser-plasma instabilities.
关键词： hot electrons,plasma corona homogeneity,laser-plasma instabilities
更新于2025-09-23 15:21:01
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Plasmonic Hot-Electron-Induced Control of Emission Intensity and Dynamics of Visible and Infrared Semiconductor Quantum Dots
摘要： Plasmonic hot-electron-assisted control of emission intensities and dynamics of CdSe/ZnS and infrared PbS quantum dots are studied. This is done by exploring the impact of Au/Si and Ag/Si Schottky junctions on the decay rates of such quantum dots when these junctions are placed in close vicinity of a Si/Al oxide charge barrier, forming metal-oxide plasmonic metafilms. Such structures are used to investigate how metal-dependent distributions of hot electrons and their capture via Schottky junctions can lead to suppression of the defect environments of quantum dots, offering a novel platform wherein off-resonant (non-Purcell) plasmonic processes are used to control exciton dynamics. These results show that Ag metafilms can enhance the emission of CdSe/ZnS quantum dots and elongate their lifetimes more than Au metafilms. This highlights the more efficient nature of Ag/Si Schottky junctions for hot electron excitation and capture. These results also show that such junctions can significantly suppress the nonradiative decay rates of PbS quantum dots at frequencies far from the plasmon resonances. These results demonstrate a field-effect passivation of quantum dot defects via entrapment of hot electrons and control of emission intensities and dynamics of quantum dots via the nearly frequency-independent electrostatic field of such electrons.
关键词： hot electrons,passivation,quantum dots,plasmons,metal oxide
更新于2025-09-23 15:21:01
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Establishing a new hot electrons transfer channel by ion doping in plasmonic metal/semiconductor photocatalyst
摘要： A straightforward strategy is developed to improve the injection efficiency of hot electrons in Ag/TiO2 plasmonic photocatalyst by introducing the Fe dopant. The Fe dopant energy level formed within the bandgap of TiO2 provides an extra electron transfer channel for transferring the hot electrons induced by plasmonic Ag nanoparticles.
关键词： hot electrons,plasmonic photocatalyst,Ag nanoparticles,TiO2,Fe dopant
更新于2025-09-23 15:21:01
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Tunable Localized Surface Plasmon Resonance and Broadband Visible Photo-response of Cu Nanoparticles/ZnO Surfaces
摘要： Plasmonic Cu nanoparticles (NP) were successfully deposited on ZnO substrates by atomic layer deposition (ALD) owing to the Volmer–Weber island growth mode. An evolution from Cu NP to continuous Cu films was observed with increasing the number of ALD cycles. Real and imaginary parts of the NP dielectric functions, determined by spectroscopic ellipsometry using an effective medium approach, evidence a localized surface plasmon resonance that can be tuned between the visible and near infrared ranges by controlling the interparticle spacing and size of the NP. The resulting Cu NP/ ZnO device shows an enhanced photo-response under white light illumination with good responsivity values, fast response times and stability under dark/light cycles. The significant photocurrent detected for this device is related with the hot electron generation at the NP surface and injection into the conduction band of the ZnO. The possibility of tuning the plasmon resonance together with the photo-responsivity of the device is promising in many applications related with photo-detection, photonics and photovoltaics.
关键词： atomic layer deposition,hot electrons,copper nanoparticles,photodetectors,localized surface plasmon resonance
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Hot Electrons Modulation of Third Harmonic Generation in Graphene
摘要： Hot-electrons dominate the ultrafast (～fs-ps) optical and electronic properties of metals and semiconductors and they are exploited in a variety of applications including photovoltaics and photodetection. Here we perform power-dependent third harmonic generation (THG) measurements on gated single layer graphene (SLG) and we show that hot-electrons modulate significantly the power-law dependence of THG, inducing a large deviation from the expected cubic power-law. We use a Chemical Vapor Deposition (CVD) SLG sample transferred on Fused Silica (FS) and gated by ionic liquid (IL), Fig.1(a). We excite the sample with the idler beam of an Optical Parametric Oscillator (OPO, Coherent) at a photon energy of ?ω0=0.69eV. The OPO is seeded by a mode-locked Ti:Sa laser (Coherent) with 150fs pulse duration and 80MHz repetition rate. The OPO idler spot-size is～4.7μm and the pulse duration ～300fs.
关键词： Hot electrons,nonlinear optics,third harmonic generation,graphene
更新于2025-09-23 15:19:57
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Interference microscopy study of the preplasma formed on an iron target surface exposed to high-power femtosecond laser pulses
摘要： The characteristic scale of spread of the plasma formed on the surface of a bulk iron target irradiated by a femtosecond laser pulse with an intensity of 1016 W cm–2 is measured by time-resolved interference microscopy using femtosecond pulses emitted by a Cr : forsterite laser system with an intensity contrast of 107. The chosen technique is demonstrated to be efficient in such measurements. It is shown experimentally that, as a result of laser pulse impact, the displacement of a plasma layer with a density exceeding critical does not exceed 30 nm.
关键词： interference microscopy,femtosecond pulse,electron acceleration mechanisms,hot electrons
更新于2025-09-23 15:19:57
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European Microscopy Congress 2016: Proceedings || Characterizing Localized Surface Plasmons using Electron Energy-Loss Spectroscopy
摘要： Localized surface plasmon resonances (LSPRs) are the coherent and collective oscillations of conduction band electrons at the surface of metallic nanoparticles. LSPRs are known to localize far-field light to a sub-diffraction-limited length scale, yielding an intense electric field at the particle surface. This effect has been harnessed to dramatically enhance light-matter interactions, leading to a variety of applications such as surface-enhanced Raman spectroscopy (SERS), photothermal cancer therapy and solar energy harvesting. Though a variety of near- and far-field optical methods are used to probe LSPRs, the spatial resolution of these methods is on the order of tens of nanometers, limiting their effectiveness. In contrast, electron energy loss spectroscopy (EELS) performed in a scanning transmission electron microscope (STEM) combines sub-nanometer resolving power with the capability to excite both optical-accessible and –inaccessible plasmon modes and therefore has emerged as one of the leading techniques (Figure 1). In this presentation, I will briefly introduce the STEM/EELS technique and demonstrate the power of STEM/EELS in the characterization of LSPRs. In addition to the traditional use of STEM/EELS for LSPR imaging, we have recently demonstrated that STEM/EELS can also be used to spatially map LSP-semiconductor energy transfer at the nanoscale. The future of STEM/EELS as a window into the nanoscopic world is especially promising, and we expect continued advances in the molecular, optical, materials, information, and energy sciences as a result.
关键词： Localized Surface Plasmon,Hot Electrons,Scanning Transmission Electron Microscopy,Energy Transfer,Electron Energy-Loss Spectroscopy
更新于2025-09-23 15:19:57
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Harvesting hot electrons on Au nanoparticle monolayer by efficient compensation of holes
摘要： Plasmonic metal nanoparticles (NPs), due to its unique optical properties, has been employed in various fields, including photocatalysis and surface-enhanced Raman scattering (SERS). Hot electrons generated from non-radiative decay of plasmons can be transferred to reactant molecules adsorbed on the metal surface and thus greatly facilitate photocatalytic chemical conversions under far milder conditions than conventional thermal catalysis. However, due to the ultra-fast relaxation or recombination, the number of hot electrons that can be effectively utilized is very limited. Herein, we report the efficient compensation of holes and harvesting hot electrons by adding NaBH4 or acidic Na2SO3 solution as holes scavenger to contribute for the lasting generation of hot electrons as well as active hydrogen species. A six-electron photocatalytic reduction of nitroarenes is achieved under laser illumination even on the ～80 nm Au NP self-assembled monolayer (SAM) after NaBH4 or acidic Na2SO3 solution catalytically inert are added. The role of NaBH4 or acidic Na2SO3 solution is elucidated to compensate holes rather than directly reduce the nitroarene. This concept of harvesting hot electrons by quick compensation of holes offers new opportunities for driving efficient light-to-energy conversion.
关键词： Plasmonics,SERS,Au nanoparticles,Hot electrons,Nitroarene reduction
更新于2025-09-19 17:15:36