Electron Trapping Efficiency Research Articles

Beam-driven electron-acoustic waves in auroral region of magnetosphere with superthermal trapped electrons

The propagation characteristics of nonlinear electron-acoustic (EA) waves are studied in a four-component magneto-plasma, containing inertial cold electrons, warm drifting beam electrons, trapped superthermal hot electrons, and static ions. A linear dispersion relation for EA waves is derived to analyze the impact of electron superthermality on the ω−k relation. For nonlinear analysis, a reductive perturbation formalism is adopted to solve the set of model equations in the form of a trapped Zakharov–Kuznetsov (tZK) equation. The latter is analyzed to determine the solitary structures in terms of phase portraits and exact soliton solutions showing the impact of electron trapping efficiency (γ), hot electron superthermality (κ), drifting speed, temperature and density of beam electrons, and temperature and density of cold electrons, using typical parameters from the short-duration burst of broad-band electrostatic noise emissions observed by the Viking spacecraft in the auroral region. The solitary structures propagate as positive potential pulses and become modified with superthermal trapped electrons, leading to hole (hump) in cold (hot) electron density excitations. The electric field structures of the EA waves are found to be in exact agreement with the observed solitary structures in the auroral region. It is observed that electric field strength associated with these waves decreases as the magnetic field increases. The present model can be used to understand the transport of energy and momentum between plasma particles and to comprehend magnetic reconnection region in magnetopause, where two-temperature electrons and large-amplitude parallel electrostatic waves have been reported by magnetopause multiscale observations.

Electron trapping efficiency of a magnetron sputtering cathode

A common feature of all types of magnetron sputtering (MS) assemblies is an effective confinement of electrons by an appropriate combination of electric and magnetic fields. Therefore, studying the motions of electrons in the fields of magnetron assemblies is of particular importance. Here, we systematically analyze the electrons motions in front of a typical DC MS cathode. We first calculate the profiles of the magnetron’s magnetic field for balanced and two types of unbalanced configurations. Then, we compute the profiles of the cathode’s electric field before the gas discharge and after the plasma formation. A semi-analytical model is utilized to compute the plasma potential. We then track the motions of electrons released from the target and electrons produced through impact ionization of the background gas in the prescribed fields. A Monte Carlo model is implemented to consider electron-gas collisions and a mixed boundary condition is employed to account for electron-wall interactions. The study analyzes the impact of field profiles on the cathode’s efficiency in trapping electron by examining electron escape from the magnetic trap and electron recapture at the target surface. It is shown that the presence of plasma in all configurations leads to a significant increase in the trapping efficiency and the ionization performance, as well as a decrease in the recapture probability. These effects are attributed to the high electric field developed in the cathode sheath. Moreover, we statistically analyze the trapping efficiency by illustrating the spatial distributions of electrons locations in both axial and radial dimensions. It is demonstrated that during their azimuthal drift motion, the electrons released from the middle region at the target surface have the smallest range of axial and radial locations, in all configurations in the absence of plasma. Finally, the impact of field profiles on the average energies of electrons is discussed.

Boosting H2O2 photosynthesis by accumulating photo-electrons on carbonyl active site of polyimide covalent organic frameworks

The low trapping efficiency of photogenerated electrons by the targeted reduction site seriously restricts the kinetics of H2O2 photosynthesis via two-electron oxygen reduction reaction. Here, two polyimide covalent organic frameworks (PT-COF and PB-COF) possessing carbonyl groups with different electron-trapping capacity were elaborately designed. PB-COF with electron-rich carbonyl site presented 4.22 times improvement in H2O2 formation rate up to 2044 μmol g−1 h−1, and exhibited outstanding photostability after 120 h continuous opearting. Meanwhile, solar to-chemical energy efficiency was 0.68%, representing one of advanced polymer based photocatalysts. We demonstrated electronic structure of the carbonyl active center was modulated by tuning electron attraction capability of the donor unit via increased the built-in electric field to accelerate charge separation and directional transfer. The electron-rich carbonyl site is identified to boosted H2O2 photosynthesis activity via reducing the *OOH binding energy. Our work offers a tailoring electron density of pre-designable active site strategy for enhanced solar-to-chemical energy conversion.

Crop-Specific Responses to Cold Stress and Priming: Insights from Chlorophyll Fluorescence and Spectral Reflectance Analysis in Maize and Soybean.

This study aimed to investigate the impact of cold stress and priming on photosynthesis in the early development of maize and soybean, crops with diverse photosynthetic pathways. The main objectives were to determine the effect of cold stress on chlorophyll a fluorescence parameters and spectral reflectance indices, to determine the effect of cold stress priming and possible stress memory and to determine the relationship between different parameters used in determining the stress response. Fourteen maize inbred lines and twelve soybean cultivars were subjected to control, cold stress, and priming followed by cold stress in a walk-in growth chamber. Measurements were conducted using a portable fluorometer and a handheld reflectance instrument. Cold stress induced an overall downregulation of PSII-related specific energy fluxes and efficiencies, the inactivation of RCs resulting in higher energy dissipation, and electron transport chain impairment in both crops. Spectral reflectance indices suggested cold stress resulted in pigment differences between crops. The effect of priming was more pronounced in maize than in soybean with mostly a cumulatively negative effect. However, priming stabilized the electron trapping efficiency and upregulated the electron transfer system in maize, indicating an adaptive response. Overall, this comprehensive analysis provides insights into the complex physiological responses of maize and soybean to cold stress, emphasizing the need for further genotype-specific cold stress response and priming effect research.

Interfacial Electrostatic-Interaction-Enhanced Photomultiplication for Ultrahigh External Quantum Efficiency of Organic Photodiodes.

A photomultiplication-type organic photodiode (PM-OPD), where an electric double layer (EDL) is strategically embedded, is demonstrated, with an exceptionally high external quantum efficiency (EQE) of 2210000%, responsivity of 11200 A W-1 , specific detectivity of 2.11 × 1014 Jones, and gain-bandwidth product of 1.92 × 107 Hz, as well as high reproducibility. A polymer electrolyte, poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))dibromide is employed as a work-function-modifying layer of indium tin oxide (ITO) to construct an EDL-embedded Schottky junction with p-type polymer semiconductor, poly(3-hexylthiophene-diyl), resulting in not only advantageous tuning of the work function of ITO but also an enhancement of the electron-trapping efficiency due to electrostatic interaction between exposed cations and trapped electrons within isolated acceptor domains. The effects of the EDL on the energetics of the trapped electron states and thus on the gain generation mechanism are confirmed by numerical simulations based on the drift-diffusion approximation of charge carriers. The feasibility of the fabricated high-EQE PM-OPD especially for weak light detection is demonstrated via a pixelated prototype image sensor. It is believed that this new OPD platform opens up the possibility for the ultrahigh-sensitivity organic image sensors, while maintaining the advantageous properties of organics.

Transmission and Trapping of Low-Energy (1–10 eV) Electrons in Crystalline Ice Films

We studied the interactions between low-energy (1–10 eV) electrons and a crystalline ice film in a low fluence condition, where incident electrons interacted mostly with the pristine ice lattice. The electron beams were irradiated onto an ice film sample of large thickness (>100 monolayers) at 95 K. The kinetic energy and flux of incident electrons were maintained constant by applying an offset bias potential to the sample to compensate the charging voltage of an ice film developed by electron trapping. A Kelvin work-function probe was used to measure the charging voltage and estimate the electron trapping efficiency. The measurements for ice films with different thicknesses showed that low energy electrons transmitted through the ice films very efficiently. When electrons were trapped in the ice films, the trapping occurred preferentially at the surface of ice films. The electron trapping cross-section for the ice surface was estimated to be ≤(2.6 ± 0.3) × 10–23 m2 at the incident electron energy of 1–10 eV. The electron trapping cross-section for the ice interior was below ∼10–25 m2. In comparison, adsorbed SO2 and CFCl3 molecules on the ice surface were able to trap incident electrons much more efficiently than the surface water molecules, with corresponding cross sections of (1.1 ± 0.4) × 10–21 m2 and (2.8 ± 0.3) × 10–21 m2, respectively.

Evolution of energy spectra of the electronic component for plasmoids generated under autoresonance conditions in a long magnetic mirror

We performed a 3D numerical simulation of plasmoid generation with a relativistic electron component under gyromagnetic autoresonance conditions in a long mirror trap. We studied the process of plasmoid formation, the spaciotemporal dynamics and the evolution of the energy spectra of the electron component of the plasma and the efficiency of electron trapping as a function of the experimental parameters.

Dust ion‐acoustic solitons with trapped q‐non‐extensive electrons, dissipative processes, and streaming ions

The characteristics of dust ion‐acoustic waves (DIAWs) that are excited because of streaming ions and hot q‐non‐extensive electrons obeying a vortex‐like distribution are investigated. By exploiting a pseudo‐potential technique, we have derived an energy integral equation. The presence of non‐extensive q‐distributed hot trapped electrons and a streaming ion beam has been shown to influence soliton structure quite significantly. The evolution of the soliton‐like perturbations in complex plasmas, taking into account the dissipation processes, are also investigated, obtained by numerically solving the modified Schamel, equation whose widths are dependant on electron trapping efficiency β. Our illustrations indicate that compressive DIAWs develop in this plasma. As the plasmas in reality have a relative flow, such an analysis can be used to understand the DIA solitary structures observed in the mesospheric noctilucent clouds.

Slow electron acoustic double layer (SEADL) structures in bi-ion plasma with trapped electrons

The properties of ion acoustic double layer (IADL) structures in bi-ion plasma with electron trapping are investigated by using the quasi-potential analysis. The κ-distributed trapped electrons number density expression is truncated to some finite order of the electrostatic potential. By utilizing the reductive perturbation method, a modified Schamel equation which describes the evolution of the slow electron acoustic double layer (SEADL) with the modified speed due to the presence of bi-ion species is investigated. The Sagdeev-like potential has been derived which accounts for the effect of the electron trapping and superthermality in a bi-ion plasma. It is found that the superthermality index, the trapping efficiency of electrons, and ion to electron temperature ratio are the inhibiting parameters for the amplitude of the slow electron acoustic double layers (SEADLs). However, the enhanced population of the cold ions is found to play a supportive role for the low frequency DLs in bi-ion plasmas. The illustrations have been presented with the help of the bi-ion plasma parameters in the Earth's ionosphere F-region.

Ion acoustic solitons in an electronegative plasma with electron trapping and nonextensivity effects

The impact of electron trapping and nonextensivity on the low frequency ion acoustic solitary waves in an electronegative plasma is investigated. The energy integral equation with the Sagdeev truncated approach is derived, which is then solved with the help of suitable parameters and necessary conditions to get the solitary structures. The minimum Mach (M) number needed to calculate the solitary structures is found to be varying under the impact of trapping efficiency determining factor β and entropic index q. The results have been illustrated with the help of physically acceptable parameters and the amplitude of nonlinear solitary structures is found to be modified significantly because of electron trapping efficiency β and entropic index q. This study has been made with reference to Laboratory observation, which can also be helpful in Space and astrophysical plasmas where electronegative plasmas have been reported.

Double layers and solitary structures in electron-positron-ion plasma with Kappa distributed trapped electrons

The effect of electron trapping in an electron-positron-ion plasma is modeled with κ-distributed electrons. The trapped electron number density is truncated to some finite order of the electrostatic potential Φ. Small amplitude solitary structures with Sagdeev potential approach and reductive perturbation method (through Schamel equation) are found to be modified under the impact of superthermality index κ and trapping efficiency β. A modified Schamel equation which gives rise to the small amplitude double layers (SIADLs) is obtained. The role of various plasma parameters in particular, the superthermality index, the positron concentration, and the electron trapping efficiency on the small amplitude ion acoustic double layers (SIADLs) has been investigated. It can be inferred from this investigation that these parameters play modifying character in the formation of nonlinear structures like solitary waves and SIADLs in e–p–i plasma.

Influence of an external axial magnetic field on betatron radiation from the interaction of a circularly polarized laser with plasma

In this paper, theoretical analyses and numerical calculations are carried out to investigate the influence of an externally applied axial constant magnetic field on electrons' betatron radiation when an ultra-short, circularly polarized laser pulse of a peak intensity I0 = 5 × 1019 W/cm2 propagates in plasma of an electron density n0 = 1020/cm3. Ring-like x-ray radiation is emitted from the electrons' betatron oscillations. The applied magnetic field can modulate the resonance process between an electron's betatron oscillation and the laser electric field, and the electron energy gain from the direct laser acceleration is thus changed. When a magnetic field of strength B0=3 × 103 T is applied, which is in anti-parallel to the self-generated axial magnetic field, both the trapping efficiency of electrons by the wakefield and the maximum accelerated energy are increased. The maximum electron energy, the peak of angular radiation, and the total radiation energy are increased by 11.0%, 45.6%, and 41.1%, respectively, and the radiation spectra are blue-shifted significantly.

Small amplitude double layers in a warm electronegative plasma with trapped kappa distributed electrons

We employ quasipotential analysis to derive the Sagdeev potential which accounts for the effect of electron trapping in a warm electronegative plasma with κ-distributed electrons. The trapped electron density is truncated to some finite order of the electrostatic potential Φ. This consequently leads to an extended KdV equation which gives rise to small amplitude double layers (SIADLs). The effects of various plasma parameters, e.g., superthermality index, the electron trapping efficiency, the mass ratio of negative to positive ion, the number density ratio of electron to positive ion, and temperature ratio of positive ion to electron on the small amplitude ion acoustic double layers (SIADLs), have been investigated. It has been found that these parameters have a significant modifying role in the SIADLs.

Room-temperature mid-infrared photodetector in all-carbon graphene nanoribbon-C_60 hybrid nanostructure

Graphene has emerged as a promising candidate for optoelectronic applications due to its broadband absorption and ultrafast carrier mobility. However, its prominent disadvantages, i.e., the zero bandgap and ultrafast carrier lifetime, limit its usage in optoelectronic applications. Although patterning graphene into nanoribbons is an effective strategy to open a bandgap, it still remains a challenge to reduce the surface and edge scattering and recombination of the photoexcited carriers. Here, we fabricated an all-carbon graphene nanoribbon-C60 hybrid nanostructure that is able to achieve a high photoresponsivity of 0.4 A/W under mid-infrared laser illumination at room temperature. Such a high performance is achieved through the high electron trapping efficiency of the C60 film as deposited onto 10 nm wide graphene nanoribbons. This all-carbon hybrid photodetector paves the way toward achieving flexible and broadband photodetectors for various applications such as imaging, remote optical sensing, and infrared camera sensors.

Controllable synthesis and photocatalytic activity of Ag/BiOI based on the morphology effect of BiOI substrate

Two series of morphology-dependent Ag/BiOI composites were successfully synthesized by using a facile photodeposition method. The typical BiOI 2D plate and 3D flower with exposed (001) facets were applied as substrates. The morphology effects of BiOI on the growth of Ag quantum dots and the photocatalytic activity of Ag/BiOI were discussed. During the photodeposition process, weak separation efficiency of BiOI 2D plate facilitated the formation of larger sized Ag quantum dots which displayed higher electron trapping efficiency and resulted in higher photocatalytic activity than those with smaller size on BiOI 3D flower. The pseudo-first-order rate constants kapp of BiOI plate and BiOI flower were 0.32 and 0.85h−1 while the corresponding activities of Ag/BiOI were further increased 3.25 and 1.11 times for degrading methyl orange. It is a promising way to regulate the activity of Ag/BiOI even the universal noble metal/semiconductor composite through controlling the morphology of semiconductor substrate.

High power pulsed magnetron sputtering: A method to increase deposition rate

High power pulsed magnetron sputtering (HPPMS) is a state-of-the-art physical vapor deposition technique with several industrial applications. One of the main disadvantages of this process is its low deposition rate. In this work, the authors report a new magnetic field configuration, which produces deposition rates twice that of conventional magnetron's dipole magnetic field configuration. Three different magnet pack configurations are discussed in this paper, and an optimized magnet pack configuration for HPPMS that leads to a higher deposition rate and nearly full-face target erosion is presented. The discussed magnetic field produced by a specially designed magnet assembly is of the same size as the conventional magnet assembly and requires no external fields. Comparison of deposition rates with different power supplies and the electron trapping efficiency in complex magnetic field arrangements are discussed.

Investigation of e-h Trapping Efficiency in Eu3+ Doped YPO4 Using VUV Spectroscopy

Absorption of Vacuum Ultraviolet (VUV) radiation creates excited e – h pairs in rare – earth doped phosphors that can either be trapped by a defect state (killer) or Ln3+ activator. The e – h trapping efficiency by Ln3+ is proportional to the rate of transfer to the activators. Recent work on YBO3:Eu3+ nano-sized particles indicate that with decreasing particle size, there is an increase in loss of energy to surface states [1]. Micron-sized Ln3+ doped YBO3 particles seem to have no surface loss effects. Our ultimate goal is to study particle size effects on surface loss and trapping efficiency in Ln3+ doped phosphor compounds. To develop a point of reference for surface loss and trapping efficiency for other nano-sized Ln3+ doped phosphor compounds, the corresponding micron-sized phosphors must be analyzed first. Thus, the e - h trapping efficiencies under VUV excitation have been determined from absorbance and excitation spectra for micron-sized Ln3+ doped YBO3, YPO4, and LaPO4. Several of these phosphor compounds contain multiple d(Ln3+) and or a Ln2+ - charge transfer (CT) state in the band gap for e - h trapping to occur. For a single CT strap state, a unique method for estimating the transfer efficiency under VUV excitation has been developed [2], and we have recently proposed a method to determine transfer efficiencies under VUV excitation for each of the individual trap states for Ln3+ doped phosphor compounds that contain multiple trap states [3]. Treating these data using accepted kinetic models allows us to calculate relative trapping efficiencies as well as the degree of surface loss. To understand the trapping mechanism, the Ln3+ energy levels relative to host states must be taken into consideration. We have developed an energy level scheme of Ln2+ and Ln3+ ground states relative to the valence band maximum (VBM) of Ln3+ doped compounds using techniques proposed by Dorenbos and Thiel [4,5,6]. Results indicate that if the Ln3+ ground state is higher in energy than the VBM, and d – orbitals are in the band gap, e - h trapping by the activator will form a 5d(Ln3+) state. The e - h trapping efficiency shows a positive linear correlation with the energy difference of the Ln3+ ground state and VBM. That is, the observed trapping efficiency appears to be dictated by hole trapping efficiency of the Ln3+ ground state for the corresponding activators. For the activators with the Ln3+ ground state approximately equivalent to or lower in energy relative to the VBM, and a Ln2+ ground state CT that is in the band gap, a linear correlation is observed between the trapping efficiency and the difference in energy between the CT state and conduction band edge (CBE). In this case, a CT state is formed and the trapping efficiency must be dictated by the electron trapping efficiency for the corresponding activator. Having completed a preliminary study of the micron – sized materials, data will be presented on our studies of surface loss effects in the nano – sized materials.

Impact of Charge Trapping Layer Thickness and New Trade-Off in Performance Characteristics of 3-D SONOS Devices

We evaluate the impact of silicon nitride (SiN) layer thickness in BiCS-like 3-D SONOS devices via standard and advanced characterization techniques, based on program (erase) efficiency measurements. SiN thickness below 4 nm strongly impacts electron trapping efficiency, resulting in degraded program operation but enhanced erase saturation level and hence giving rise to a new program-erase trade-off. An optimal 4 nm SiN thickness is assessed for proper MLC operation.

Charge Trapping and Detrapping in nc-RuO Embedded ZrHfO High-k Thin Film for Nonvolatile Memory Applications

The charge trapping and detrapping characteristics of the nc-RuO embedded Zr-doped HfO2 (ZrHfO) high-k MOS capacitor have been studied. The memory function of the capacitor is mainly contributed by hole trapping during the forward sweep from −9 V to +9 V and electron trapping during the backward sweep from +9 V to −9 V. The time- and bias-dependent stress test results show that the hole-trapping efficiency is higher than the electron-trapping efficiency due to different charge trapping sites and supply mechanisms. In order to delineate the detailed mechanisms, samples were characterized with the frequency-dependent conductance-voltage curves, relaxation currents, ramp-relax current measurements, and retention characteristics. Although most electrons are deeply trapped in the bulk nc-RuO sites, a portion of holes are loosely trapped at the nc-RuO/ZrHfO interface due to the lost of the short-term retention capability. The deeply-trapped holes and electrons were strongly held for a long period.

Investigating the degradation behavior caused by charge trapping effect under DC and AC gate-bias stress for InGaZnO thin film transistor

This letter investigates the degradation mechanism of amorphous indium-gallium-zinc oxide thin-film transistors under gate-bias stress. The larger Vt shift under positive AC gate-bias stress when compared to DC operation indicates that an extra electron trapping mechanism occurs during rising/falling time during the AC pulse period. In contrast, the degradation behavior under illuminated negative gate-bias stress exhibits the opposite degradation tendency. Since electron and hole trapping are the dominant degradation mechanisms under positive and illuminated negative gate-bias stress, respectively, the different degradation tendencies under AC/DC operation can be attributed to the different trapping efficiency of electrons and holes.