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Measurement and Evaluation of Local Surface Temperature Induced by Irradiation of Nanoscaled or Microscaled Electron Beams
摘要： Electron beams (e-beams) have been applied as detecting probes and clean energy sources in many applications. In this work, we investigated several approaches for measurement and estimation of the range and distribution of local temperatures on a subject surface under irradiation of nano-microscale e-beams. We showed that a high-intensity e-beam with current density of 105-6 A/cm2 could result in vaporization of solid Si and Au materials in seconds, with a local surface temperature higher than 3000 K. With a lower beam intensity to 103-4 A/cm2, e-beams could introduce local surface temperature in the range of 1000–2000 K shortly, causing local melting in metallic nanowires and Cr, Pt, and Pd thin films, and phase transition in metallic Mg-B films. We demonstrated that thin film thermocouples on a freestanding Si3N4 window were capable of detecting peaked local surface temperatures up to 2000 K and stable, and temperatures in a lower range with a high precision. We discussed the distribution of surface temperatures under e-beams, thermal dissipation of thick substrate, and a small converting ratio from the high kinetic energy of e-beam to the surface heat. The results may offer some clues for novel applications of e-beams.
关键词： Vaporization,Local temperature,Nanoscale thermometry,Transmission electron microscopy,Thin film thermocouple,Energy converting,Electron beam,Scanning electron microscopy,Melting point
更新于2025-09-11 14:15:04
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Design and Measurement of a Terahertz Double Staggered Grating Waveguide With an Arc-Shaped Beam Tunnel
摘要： A millimeter-waveband double staggered grating waveguide (DSGW) with an arc-shaped beam tunnel was previously proposed for sheet beam traveling wave tubes. In this article, the design, fabrication, and cold test of a terahertz band DSGW with an arc-shaped beam tunnel are presented. Simulations demonstrated that the novel DSGW would have a higher coupling impedance and a better beam wave interaction in comparison to the conventional DSGW with a linear-shaped beam tunnel. Beam wave interaction simulations showed that the output power and the electronic efficiency, respectively, increased from ～420 W to ～580 W and from 7.0% to 9.3% at 240 GHz. These two kinds of DSGWs were fabricated by using the nanocomputer numerical control (CNC) milling and wire cutting techniques, and their performances were cold tested by using a vector network analyzer. The measurement results were in good agreement with the simulations and demonstrated that both the traditional and novel DSGWs achieved a wide frequency bandwidth of ～40 GHz (0.22–0.26 THz) with a transmission coefficient S21 better than ?2.7/?3.0 dB and a reflection coefficient S11 lower than ?13.0/?15.7 dB, respectively.
关键词： terahertz radiation,sheet electron beam (SEB) devices,Arc-shaped beam tunnel,double staggered grating waveguide (DSGW)
更新于2025-09-11 14:15:04
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Self-assembly of single-walled carbon nanotubes arrays with different line width
摘要： Single-walled carbon nanotubes (SWNTs) are one of the most promising nanoelectronic materials, However, there are still some application challenges, including purification, regular arrangement, interconnection, and so on. There is evidence that the array assembly can improve the performance of SWNTs. In this work, we develop a line-width controllable large-scale assembly of SWNTs based on aqueous solution, using electron beam (E-beam) lithography to construct self-assembled templates. The results show that SWNTs arrays of different line-width are obtained, which is possible to design the structure of SWNTs assembly to meet different functions.
关键词： Single-walled carbon nanotubes (SWNTs),self-assembly,line-width,electron beam (E-beam) lithography
更新于2025-09-11 14:15:04
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Chemical Structure of EVA Films Obtained by Pulsed Electron Beam and Pulse Laser Ablation
摘要： Poly(ethylene-co-vinyl acetate) (EVA) films were deposited for the first time using physical methods. The chemical structure of the films obtained using two techniques, pulsed electron beam deposition (PED) and pulsed laser deposition (PLD), was studied by attenuated total reflection Fourier infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Whilst significant molecular degradation of the EVA films was observed for the PLD method, the original macromolecular structure was only partially degraded when the PED technique was used, emphasizing the superiority of the PED method over PLD for structurally complex polymers such as EVA. Optical and scanning electron microscopic observations revealed compact and smooth EVA films deposited by pulsed electron beam ablation as opposed to heterogeneous films with many different sized particulates obtained by PLD.
关键词： chemical structure analysis,poly(ethylene-co-vinyl acetate),pulsed laser deposition,pulsed electron beam deposition
更新于2025-09-11 14:15:04
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Spin-polarization effects of an ultrarelativistic electron beam in an ultraintense two-color laser pulse
摘要： Spin-polarization effects of an ultrarelativistic electron beam head-on colliding with an ultraintense two-color laser pulse are investigated comprehensively in the quantum radiation-dominated regime. We employ a Monte Carlo method, derived from the recent work of Li et al. [Phys. Rev. Lett. 122, 154801 (2019)], to calculate the spin-resolved electron dynamics and photon emissions in the local constant field approximation. We find that electron radiation probabilities in adjacent half cycles of a two-color laser field are substantially asymmetric due to the asymmetric field strengths and, consequently, after interaction the electron beam can obtain a total polarization of about 11% and a partial polarization of up to about 63% because of radiative spin effects, with currently achievable laser facilities, which may be utilized in high-energy physics and nuclear physics. Moreover, the considered effects are shown to be crucially determined by the relative phase of the two-color laser field and robust with respect to other laser and electron-beam parameters.
关键词： radiative spin effects,Monte Carlo method,quantum radiation-dominated regime,spin-polarization,two-color laser pulse,ultrarelativistic electron beam
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || SEM based electro-optical characterization of core-shell LEDs and simulation of imaging including CL and EBIC excitation inside ensembles
摘要： Three dimensional (3D) nano- and microstructures (NAMs) are attracting a lot of attention and are discussed regarding several applications, especially in optoelectronics and sensors. For example GaN based 3D light emitting diodes (LEDs) with a core-shell geometry are supposed to have substantial advantages over conventional planar LEDs: The active area along the sidewalls of hexagonal GaN pillars can considerably be increased by high aspect ratios - leading to a lower current density inside the InGaN quantum well (QW) at the same operation current per substrate area. [1] Thus related methods are requested for characterization of local electro-optical properties with a high spatial resolution on single structures as well as in ensembles. Usually, electron microscopy is employed to investigate the geometry and properties of such 3D-NAMs and for mapping of vertical features by an SEM a certain sample tilt (e.g. about 30°) is needed. Investigation of single 3D-LEDs by electron beam induced current (EBIC) using an SEM based manipulator setup proves the presence of a pn-junction and doping type of the core and shell, while cathodoluminescence (CL) gives an insight to the optical properties of the QW [2]. But in contrast to SEM on planar regions the interactions of the electron probe are significantly affected by the 3D geometry and the surrounding of the NAMs. In ensembles of 3D-NAMs a certain portion of incident electrons are scattered into neighbor structures and conventional SEM signals (SE, BSE, CL, X-ray emission) are partly shadowed. This interaction is affecting the SEM imaging contrast and the probed signal also includes contributions which are not related to the material properties at the electron beam spot. As such parasitic signals are generated quite close to the original region of the interaction most (global) SEM detectors cannot separate them from the original source. In particular scattering events occur in an enlarged volume of the sample (of the substrate and NAMs) leading to a reduced excitation density and parasitic effects, e.g. this causes a significant contribution of defect related yellow luminescence (YL) We present results of InGaN/GaN core-shell LEDs obtained with an FE-SEM which is equipped with SE, In-Beam SE, low-kV BSE, EBIC and monochromatic CL detection as well as a piezo controlled manipulator setup, see Figure 1. A modified parabolic collection mirror enables measuring luminescence from planar samples up to 4’’ in a tilted view up to 30°. For a quantitative interpretation of CL and EBIC measurement values and image contrasts, the physical modeling of SEM images and spatially resolved energy transfer by a probe spot is necessary. This is performed using the simulation program MCSEM [3]. It models the different stages of image formation and generates SEM images of complex NAM shapes using e.g. GaN as model material. Aspects of the simulation are the electron probe formation, a 3D model of the specimen structure, the interaction of electron probe and solid state by means of scattering trajectories, the emission of secondary electrons, and different types of electron detectors, see Figure 2 and Figure 3. An insight to CL and EBIC imaging is gained by evaluating the scattering energy deposited in a distinct volume inside the NAMs as an imaging signal - this is related to the generation rate of electron-hole pairs inside the respective volume of the semiconductor. Consent to the experiments this simulation reveals an edge contrast and shadowing of signals by the ensemble as well as scattering of primary electrons inside the ensemble of 3D-NAMs. A quantitative comparison is possible by the absorbed current (EBAC). Artefacts of the EBIC are also demonstrated by the simulation, in particular edge contrast by a reduced generation rate and parasitic signals by scattering from neighbor structures.
关键词： EBIC,cathodoluminescence,electron beam induced current,SEM simulation,core-shell LED
更新于2025-09-11 14:15:04
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Polarized Positron Beams via Intense Two-Color Laser Pulses
摘要： The generation of ultrarelativistic polarized positrons during the interaction of an ultrarelativistic electron beam with a counterpropagating two-color petawatt laser pulse is investigated theoretically. Our Monte Carlo simulation, based on a semiclassical model, incorporates photon emissions and pair productions, using spin-resolved quantum probabilities in the local constant field approximation, and describes the polarization of electrons and positrons for the pair production and photon emission processes, as well as the classical spin precession in between. The main reason for the polarization is shown to be the spin asymmetry of the pair production process in strong external fields, combined with the asymmetry of the two-color laser field. Employing a feasible scenario, we show that highly polarized positron beams, with a polarization degree of ζ ≈ 60%, can be produced in a femtosecond timescale, with a small angular divergence, ～74 mrad, and high density, ～1014 cm?3. The laser-driven polarized positron source raises hope for providing an alternative for high-energy physics studies.
关键词： polarized positron beams,ultrarelativistic electron beam,local constant field approximation,spin-resolved quantum probabilities,high-energy physics,Monte Carlo simulation,two-color laser pulses
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [AIP Publishing INTERNATIONAL CONFERENCE ON PHOTONICS, METAMATERIALS & PLASMONICS: PMP-2019 - Noida, India (14–16 February 2019)] INTERNATIONAL CONFERENCE ON PHOTONICS, METAMATERIALS & PLASMONICS: PMP-2019 - Stabilization of plane polarized Alfven waves by anomalous Doppler resonance
摘要： This work presents non-linear decay of plane polarized Alfven wave via anomalous Doppler resonance with an electron beam in a magnetized plasma. First order perturbation theory has been employed to derive the expressions for dispersion relation of Alfven waves and their growth rate. Numerical calculations have also been carried out for growth rate and unstable mode frequencies for typical plasma parameters. There exists two modes of wave propagation, one having frequency < ωci corresponds to Alfven wave, and the other has frequency approaching ωce which corresponds to electron cyclotron wave. The waves interact with the electron beam via normal and anomalous Doppler resonance. The normal resonance interaction increases the frequency of plane polarized Alfven wave but shows no growth or decay in amplitude. However, in anomalous resonance interaction the frequency remains unchanged and the wave stabilizes. The variation of frequency and growth rate with magnetic field and number density of plasma electrons is also discussed in the present paper. The phase velocity and the unstable frequency of the wave decrease with an increase in the number density of plasma electrons. The results of our work are applied to explain some of the experimental observations.
关键词： anomalous Doppler resonance,magnetized plasma,Alfven waves,growth rate,electron beam
更新于2025-09-11 14:15:04
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Generation of high-charge electron beam in a subcritical-density plasma through laser pulse self-trapping
摘要： To maximize the charge of a high-energy electron beam accelerated by an ultra-intense laser pulse propagating in a subcritical plasma, the pulse length should be longer than both the plasma wavelength and the laser pulse width, which is quite different from the standard bubble regime. In addition, the laser–plasma parameters should be chosen to produce the self-trapping regime of relativistic channeling, where the diffraction divergence is balanced by the relativistic nonlinearity such that the laser beam radius is unchanged during pulse propagation in a plasma over many Rayleigh lengths. The condition for such a self-trapping regime is the same as what was empirically found in several previous simulation studies in the form of the pulse width matching condition. Here, we prove these findings for a subcritical plasma, where the total charge of high-energy electrons reaches the multi-nC level, by optimization in a 3D PIC simulation study and compare the results with an analytic theory of relativistic self-focusing. A very efficient explicitly demonstrated generation of high-charge electron beams opens a way to a high-yield production of gammas, positrons, and photonuclear particles.
关键词： relativistic channeling,high-charge electron beam,subcritical-density plasma,laser pulse self-trapping,3D PIC simulation
更新于2025-09-11 14:15:04
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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) - Deterministic Integration of Quantum Dots into On-Chip Multi-Mode Interference Couplers Via in-Situ Electron Beam Lithography
摘要： On-chip quantum optical circuits offer superior performance and scalability compared to bulky optical setups. Additionally, the up-scaling of quantum systems will foster the realization of photonic quantum computers to outperform their classical counterparts. In this context, the deterministic integration of quantum emitters into on-chip photonic elements is crucial for the implementation of scalable on-chip quantum circuits. Recent activities in this field include hybrid QD-waveguides for enhanced photon in-coupling [1] and first, rather tedious steps towards the controlled integration of QDs using multistep-lithography [2] as well as AFM tip transfer [3]. Here we report on the deterministic integration of single quantum dots (QD) into on-chip beam splitters using in-situ electron beam lithography (EBL) [4]. In this single-step technique, photonic building blocks are patterned by means of EBL on top of chosen QDs immediately after spatially and spectrally pre-characterizing QDs by means of cathodoluminescence mapping at cryogenic temperatures (~10 K) [5]. The used in-situ EBL technology platform allows for the realization of complex on-chip quantum circuits with high process yield (see Fig. 1(a-d)). To underline the high potential of this method we realize 50/50 coupling elements connected to waveguide sections with deterministically integrated QDs (see Fig. 1(e)). The couplers act as central building blocks of on-chip quantum circuits and we chose a robust design based on tapered multimode interference (MMI) splitters which feature relaxed fabrication tolerances and a constant 50/50 splitting ratio. We demonstrate the functionality of the deterministic QD-waveguide structures by high-resolution μPL spectroscopy and by studying the photon cross-correlation between the two MMI output ports (Port 1 and Port 2 in Fig. 1(e)). The latter confirms single-photon emission and on-chip splitting associated with g(2)(0) < 0.5. Present work focusses on the deterministic realization of heterogeneous integrated quantum photonic devices and multi-QD quantum circuits allowing for on-chip Hong-Ou-Mandel experiments.
关键词： on-chip quantum circuits,quantum dots,photonic quantum computers,electron beam lithography,quantum emitters
更新于2025-09-11 14:15:04