Electron Transport Parameters Research Articles

Структурные особенности, электронный и спиновый транспорт в эпитаксиальных тонких пленках иридатов

A technique for obtaining high-quality epitaxial films of iridate (SrIrO3) by high-frequency cathode sputtering on strontium titanate (SrTiO3) and neodymium gallate (NdGaO3) substrates has been developed. The structural features and the influence of mechanical stress relaxation in thin films caused by the difference in the lattice sizes of the film and the substrate have been studied using X-ray diffraction. From the analysis of diffraction data, it was found that lattice parameter deformation is observed in the film. This indicates the emergence of stresses due to the mismatch of the lattice parameters of the film and the substrate, which leads to non-uniform stress relaxation in the film. The electronic transport parameters of thin films and the excitation of spin current in SrIrO3/La0.7Sr0.3MnO3 heterostructures have been investigated.

(Invited) Numerical Simulation of an Atmospheric Pressure Streamer Discharge and Induced Chemical Reactions

Streamer discharges are a type of non-thermal plasma produced by high-voltage electrical discharges, and have great potential as highly reactive chemical reaction fields. This is mainly due to the generation of high energy electrons that produce chemically active species. The applications of non-thermal plasma have attracted considerable interest in a wide range of industries. However, each radical has a different role in the plasma application and their reaction mechanism is also different. It's therefore important to understand exactly when, where and how much of these reactive species are produced in order to improve the treatment efficiency of atmospheric pressure plasma applications. Against this background, the aim of this study is to develop a simulation model capable of accurately predicting the chemical reactions of radicals. With a sufficiently validated simulation model, it would be possible to use such a model to design chemical reaction fields.The model consists of the first-order electrohydrodynamic model for electrons and positive and negative ions within the drift-diffusion approximation. Axis-symmetric coordinates were used to simulate the streamer discharge in air at atmospheric pressure. The electron transport and source parameters were calculated using two-term bltzmann equation and published electron impact cross-sections. The chemical reaction model used in this study includes electron impact collisions (excitation, ionisation, dissociation, recombination, attachment and detachment), ion recombination and the reactions of neutrals. In order to demonstrate the validity of the simulation, the light emission of the discharge is first compared between experiment and simulation. Then the spatial and temporal variations of each radical are simulated and compared with the simulation. In this talk, I will present the process of validation and verification (V&V) of the streamer discharge simulation and then the mechanism of radical production revealed by the simulation.

Low lattice thermal conductivity induced by interlayer anharmonicity in p-type BaFZnAs compound with high thermoelectric performance

Inspired by the excellent thermoelectric (TE) performance of ZrSiCuAs-type materials, the crystal structure, thermal and electronic transport mechanisms, and TE properties of the BaFZnAs compound are explored using first-principles calculations and Boltzmann transport theory. The BaFZnAs compound is an anisotropic material, with a direct bandgap of 1.20 eV determined by the Heyd-Scuseria-Ernzerhof (HSE06) functional. The [Zn2As2]2- layer within BaFZnAs compound forms carrier transport channel, which is beneficial for high power factor. The strong out-of-plane interlayer anharmonicity of the [Ba2F2]2+ and [Zn2As2]2- layers with weak interactions leads to a low lattice thermal conductivity (1.64 W/mK at 300 K) for the BaFZnAs compound. Based on the carrier relaxation time evaluated in the consideration of multiple carrier scattering rates and electronic transport parameters, the optimal ZTs of 1.44 and 2.06 are achieved for n-type and p-type BaFZnAs compounds at 900 K, associating with the corresponding ZTs of 2.10 (0.72) and 2.64 (0.51) along the a-axis and c-axis directions. Our present work not only offers multifaceted insights into the thermal and electronic transport properties of BaFZnAs compound, but also provides a new inspiration for further TE exploration of ZrSiCuAs-type materials.

Drought-Stressed Apple Tree Grafted onto Different Rootstocks in a Coastal Sandy Soil: Link between Fast Chlorophyll a Fluorescence and Production Yield

Domesticated apple is a drought-sensitive species that spread from continental to Mediterranean temperate regions, where it can particularly experience prolonged water stress. One strategy to improve drought resistance in apple is engrafting on selected rootstocks. This study explores the potential of fast chlorophyll a fluorescence for the comparison of rootstock sensitivity to drought, looking for significant correlations with fruit productivity. The experiment was conducted in a field located in the coastal Po River Plain, Northern Italy, characterized by a loamy sandy soil, particularly prone to drought (86% sand). Mature plants of apple cv. Superchief® Sandidge engrafted on three different rootstocks (CIVP21pbr, MM106, M26) were monitored throughout the summer of 2021 and compared between irrigated and non-irrigated parcels, and at the end of the season, fruit production was evaluated. Despite soil water tension only reaching −13 kPa, the non-irrigated plants experienced a small but consistent loss of Photosystem II (PSII) activity and a lesser capacity of light energy conservation in the photosynthetic electron transport chain. The fruit weight correlated with PSII photochemical indexes recorded during early drought, particularly FV/FM and PIABS; a correlation emerged between fruit number per plant and median values of electron transport parameters, including PITOT. Although all rootstocks underwent a 40% loss of productivity, the fluorescence parameters revealed a graded susceptibility to drought, M26 > CIVP21pbr > MM106, which matched well with the plant vigour. The least drought-sensitive MM106 produced less numerous but heavier fruits than the other two rootstocks.

Simulation of 1D atmospheric pressure dielectric barrier discharge in argon

This work aims at modelling an atmospheric-pressure homogeneous barrier discharge in argon, using a time-dependent 1D fluid model coupled to the electric field and plasmo-chemical kinetic equations. The model is chosen to mimic a discharge when a sinusoidal 1 kV voltage at 10 MHz is applied to the terminals. Energy and mass transfer are considered for a macroscopic fluid representation, while energy transfer in molecular collisions and chemical reactions is treated at the microscopic level. The macroscopic model is represented by a set of coupled partial differential equations. Microscopic effects are studied within a discrete model for electronic and molecular collisions in the frame of ZDPlasKin, a plasma modelling numerical tool. The BOLSIG+ solver is employed in solving the electronic Boltzmann equation. An operator splitting technique is used to separate microscopic and macroscopic models. The spatial and temporal evolution of such species and electron transport parameters are presented and discussed.

Study of Electron Energy Distribution Function, Transport Parameters and Instability Analysis of Argon Plasma confined by a Dipole Magnet

This theoretical study is to investigate production and properties of plasma confined by a dipole magnet. A cylindrical permanent magnet (N40 grade) having a surface magnetic field of nearly 1Tesla is simulated to create a dipole magnetic field. Plasma is created by electron cyclotron resonance heating. Heating is accomplished using microwaves operating in continuous mode at 2.45 GHz and electron cyclotron resonance. The investigation is performed in systems of cylindrical geometries at varying pressures (0.5 mTorr – 1.5 mTorr). The electron temperature lies in the range of 1 - 5 eV, is hotter near the magnets and follows a downstream fashion throughout the region.Electron Energy Distribution Function (EEDF) growth investigation throughout the region was done to understand the role of magnetic field confinement. The EEDF was calculated numerically from steady state Boltzmann equation, considering plasma follows druyvesteyn distribution. Followed by analysing transport parameters such as diffusion coefficient, drift velocity, mobility, and recombination rates in plasma. A comparative study for all plots gave been done with respect to pressure. The instability analysis of elastic collisional frequency with inelastic collisions, real frequency and growth factor with wave vector has been also listed in the study.

Enhancement of thermoelectric performance in monolayer AlP3 via Ga and In doping: A first-principles study

Recently, two-dimensional (2D) triphosphides have attracted much attention in the thermoelectric field due to their semiconductor properties and excellent electronic transport properties. In our study, the performances of AlP3, Al0.5Ga0.5P3, and Al0.5In0.5P3 doped monolayers in the thermoelectric transport are studied. First, the dynamic structural stabilities of the three monolayers are verified through phonon dispersion curves. Moreover, all monolayers are indirect band-gap semiconductors, which can be used as thermoelectric materials. The results show that larger electronic relaxation time and carrier mobilities of doped monolayers lead to larger electronic transport parameters and higher dimensionless thermoelectric figure-of-merit (ZT). It is found that after doping via Ga and In, the thermoelectric performances of AlP3 are increased by 1.31–1.79 times. Our findings show that AlP3 and its doped monolayers hold significant promise as thermoelectric materials within the temperature span of 300–700 K and the doping mechanism could significantly improve the thermoelectric properties of 2D structures.

Development of a Monte Carlo tool for simulating electron transport in noble liquids

This study presents a Monte Carlo simulation tool for modeling the transportation processes of thermal electrons in noble liquids, specifically focusing on liquid argon and liquid xenon. The study aims to elucidate the microscopical mechanisms governing the drift and diffusion of electrons within the context of time projection chambers (TPCs), with detailed considerations of coherent electron-atom scattering and electric field force. The simulation tool is implemented in the Geant4 framework, allowing for the exploration of electron transport parameters, including drift velocity, longitudinal diffusion coefficient, and transverse diffusion coefficient. The simulation is validated by comparing its results for drift velocity and diffusion coefficients with experimental measurements, revealing reasonable agreement in the low to moderate electric field ranges. Discrepancies between the simulation and experimental measurements are discussed, emphasizing the necessity for enhanced cross-section calculations and high-precision sampling. Despite certain limitations, the simulation tool provides valuable insights into electron transport in noble liquids, establishing a foundation for future enhancements and applications in various research areas

Determinants of photochemical characteristics of the photosynthetic electron transport chain of maize.

The photosynthetic electron transport chain (ETC) is the bridge that links energy harvesting during the photophysical reactions at one end and energy consumption during the biochemical reactions at the other. Its functioning is thus fundamental for the proper balance between energy supply and demand in photosynthesis. Currently, there is a lack of understanding regarding how the structural properties of the ETC are affected by nutrient availability and plant developmental stages, which is a major roadblock to comprehensive modeling of photosynthesis. Redox parameters reflect the structural controls of ETC on the photochemical reactions and electron transport. We conducted joint measurements of chlorophyll fluorescence (ChlF) and gas exchange under systematically varying environmental conditions and growth stages of maize and sampled foliar nutrient contents. We utilized the recently developed steady-state photochemical model to infer redox parameters of electron transport from these measurements. We found that the inferred values of these photochemical redox parameters varied with leaf macronutrient content. These variations may be caused either directly by these nutrients being components of protein complexes on the ETC or indirectly by their impacts on the structural integrity of the thylakoid and feedback from the biochemical reactions. Also, the redox parameters varied with plant morphology and developmental stage, reflecting seasonal changes in the structural properties of the ETC. Our findings will facilitate the parameterization and simulation of complete models of photosynthesis.

Pressure-induced remarkable four-phonon interaction and enhanced thermoelectric conversion efficiency in CuInTe2

Hydrostatic pressure (P) has been regarded as an effective approach to improve the performance of thermoelectric materials. Although a positive correlation between its thermoelectric performance and pressure has been demonstrated experimentally for CuInTe2, the underlying physical mechanism remains unclear. Herewith, we investigate the inherent mechanism of hydrostatic pressure-induced electron-thermal transport properties and thermoelectric conversion efficiency for CuInTe2. It is demonstrated that the pressure limits the thermal transport behavior of heat-carrying phonons by changing phonon dispersion, where the broadening of the low-lying phonon bandwidth caused by the compression promotes the dominance of the four-phonon (4ph) scattering mechanism, especially at high temperatures. In addition, the power factor has achieved a huge net increase through the convergence of the valence band edge despite the presence of strong coupling between electron transport parameters. Such bidirectional optimization gives rise to a remarkable enhancement of thermoelectric conversion efficiency. Our work highlights the significant effect of pressure-induced 4ph interaction in CuInTe2, which brings deeper insights into the behavior of thermoelectric materials under extreme pressure environments.

MATOQ: a Monte Carlo simulation of electron transport in environmental-friendly gas mixtures for Resistive Plate Chambers

The increasing interest in environmental-friendly gas mixtures for gaseous particle detectors, especially tetrafluoropropene-based gas mixtures for Resistive Plate Chambers (RPCs), has prompted in recent years the need for simulating electron transport coefficients and reaction rates in these mixtures. MATOQ is a Monte Carlo simulation program that calculates electron transport parameters, specifically designed for studying and optimizing environmental-friendly gas mixtures for RPCs. Unlike other existing codes, MATOQ allows for the simulation of electron avalanches by including the effect of space charge electric field, which can significantly impact the avalanche evolution in gaseous detectors such as RPCs. After the validation of the MATOQ simulation in the temporal and spatial growth configurations, we present the electron transport coefficients and the reaction rates in tetrafluoropropene-based gas mixtures, which may represent a valid alternative to the standard gas mixtures currently used for RPCs.

Effect of ZnO in various alcohols on photoelectric characteristics of OSC

The paper presents the results of a study of the effect of alcohols on the electron transport of the ETL layer of a ZnO polymer solar cell with an inverted structure. To obtain films, zinc acetate was dissolved under the same experimental conditions in isopropanol, butanol and ethanol. According to the SEM data, it was found that the use of various alcohol solvents in the synthesis of the film shows a change in the morphology of the surface. The observed changes in the interface of the surface of the films are associated with the formation of ZnO aggregates depending on the polarity used of the alcohols. It is shown that the optical width of the ZnO band gap also depends on alcohol solvents. It is shown that the aggregation of ZnO has an effect on the electron transport and efficiency of the polymer solar cell. The voltage characteristics of the solar cells FTO/ ZnO/P3HT: IC60MA/PEDOT: PSS/Ag were measured. It is shown that the smallest aggregation of ZnO is observed in Isopropanol, in which the organic cell showed the highest efficiency of converting solar energy into electrical energy. The polymer solar cell has been the efficiency 2.5 %. From the obtained ETL impedance measurement data, the ZnO based layer obtained in Ethanol has the lowest electron transport parameters. This is due to the high degree of aggregation of ZnO, as a result of which the resistance to increases of the interface ZnO/FTO. The solar cells based ZnO in Ethanol demonstrated an efficiency value of 0.9 % compared to ZnO in Butanol with an efficiency of 1.6 %.

Structural arrangement and improved thermoelectric figure of merit in hexagonal SiX (X = N, P, As, Sb, Bi) monolayers: understanding from first-principles calculations

Materials with thermoelectric (TE) efficiencies comparable to Carnot efficiency are desirable for applications in devices that use TE effects to produce electricity from heat. The figure of merit of a TE material is a measure of its efficiency. This quantity is determined by the intricate interplay of electronic and thermal transport parameters. Layered materials at low dimensions, such as 2D monolayers, have been in focus with regard to the quest for new TE materials. Group III–VI semiconductors in their 2D monolayers have exhibited fascinating TE properties. Naturally, it is expected that isoelectronic IV–V semiconductors will possess similar novelty. In this work, we have investigated the electronic, dynamical and TE properties of IV–V monolayer SiN, SiP, SiAs, SiSb and SiBi using first-principles electronic structure methods in conjunction with the semiclassical Boltzmann transport theory. Unlike previous studies, here the focus was to compute and analyse the effects of structural arrangements on TE properties. We found that upon consideration of an alternative stacking arrangement in the systems, significant changes occur in the transport phenomena, leading to a large figure of merit and thus TE efficiency. A comprehensive comparative analysis is presented to interpret the results. This work bears significance in the fact that it demonstrates a very important structure–property relationship aspect for these compounds that has been overlooked so far, and this approach may lead to the discovery of new TE materials with desirable efficiencies.

Thermoelectric performance of Zintl compound KMgBi with layered structure

Zintl compounds are potential candidates for thermoelectric (TE) materials because of their excellent electronic transport combined with low thermal conductivity. We have systematically investigated the thermal, electronic transport, and TE properties of the anisotropic orthorhombic KMgBi crystal on the basis of first-principles calculations together with self-consistent phonon theory, the compressed sensing technique, and the Boltzmann transport equation. When predicting electron transport parameters, we take into account the impacts of acoustic deformation potential scattering, polar optical phonon scattering, and ionized impurity scattering on electron relaxation times. Strikingly, the layered structure of the Zintl compound KMgBi results in the material exhibiting strong anisotropy. This layered structure provides a good transport channel for electrons along the a (b)-axis, which results in a large difference in electrical conductivity and thermal conductivities between the a (b)-axis and the c-axis. Because of the high power factor obtained along the a (b)-axis, the figure of merit (ZT) is expected to reach 1.5 at 600 K and KMgBi is a promising candidate for high-temperature TE applications.

Strain Tunable Thermoelectric Material: Janus ZrSSe Monolayer

Thermoelectric (TE) performance of the Janus ZrSSe monolayer under biaxial strain is systematically explored by the first-principles approach and Boltzmann transport theory. Our results show that the Janus ZrSSe monolayer has excellent chemical, dynamical, thermal, and mechanical stabilities, which provide a reliable platform for strain tuning. The electronic structure and TE transport parameters of the Janus ZrSSe monolayer can be obviously tuned by biaxial strain. Under 2% tensile strain, the optimal power factor PF of the n-type-doped Janus ZrSSe monolayer reaches 46.36 m W m-1 K-2 at 300 K. This value is higher than that of the most classical TE materials. Under 6% tensile strain, the maximum ZT values for the p-type- and n-type-doped Janus ZrSSe monolayers are 4.41 and 4.88, respectively, which are about 3.83 and 1.49 times the results of no strain, respectively. Such high TE performance can be attributed to high band degeneracy and short phonon relaxation time under strain, causing simultaneous increase of the Seebeck coefficient and suppression of the phonon thermal transport. Present work demonstrates that the Janus ZrSSe monolayer is a promising candidate as a strain-tunable TE material and stimulates further experimental synthesis.

Correlation of rattlers with thermal transport and thermoelectric performance.

The presence of rattlers in the host-guest structure has sparked great interest in the field of thermoelectrics, as it allows for the suppression of thermal transport in materials through vigorous anharmonic vibrations. This work predicts a ternary half-Heusler compound, LiAgTe, with good thermoelectric properties and high-temperature stability, which possesses a host-guest structure. Furthermore, it provides a detailed analysis of the role of rattlers in the transport process. By microscopically exploring rattlers, we have revealed that rattlers (Ag atoms), while suppressing the thermal transport properties of the host framework, provide a significant enhancement of the electronic transport capability through the provision of nearly free weakly bound electrons. Using self-consistent phonon theory combined with compressive sensing lattice dynamics method, we captured the exact lattice thermal conductivity considering quartic anharmonicity and four-phonon scattering, and obtained the electronic transport parameters through the calculation of τe, which includes full anisotropic acoustic deformation potential scattering, polar optical phonon scattering, and ionized impurity scattering. We systematically dissected the role of rattlers in the host-guest structure by combining methods such as electron local function, Bader charge density, and Vibration visualization. The anharmonic vibrations of rattlers enhance the temperature response of scattering, resulting in rapid deterioration of thermal transport at high temperatures. Moreover, the extended d-orbital electrons of the rattlers, together with the p-orbital electrons of the Te atom in the host framework, result in the coexistence of maximum degeneracy and high dispersion bands in the valence band, which greatly enhances the electronic transport properties.

Tailoring Interfacial Charge Transfer for Optimizing Thermoelectric Performances of MnTe‐Sb2Te3 Superlattice‐Like Films

AbstractInterfacial charge transfer has a vital role in tailoring the thermoelectric performance of superlattices (SLs), which, however, is rarely clarified by experiments. Herein, based on epitaxially grown p‐type (MnTe)x(Sb2Te3)y superlattice‐like films, synergistically optimized thermoelectric parameters of carrier density, carrier mobility, and Seebeck coefficient are achieved by introducing interfacial charge transfer, in which effects of hole injection, modulation doping, and energy filtering are involved. Carrier transport measurements and angle‐resolved photoemission spectroscopy (ARPES) characterizations reveal a strong hole injection from the MnTe layer to the Sb2Te3 layer in the SLs, originating from the work function difference between MnTe and Sb2Te3. By reducing the thickness of MnTe less than one monolayer, all electronic transport parameters are synergistically optimized in the quantum‐dots (MnTe)x(Sb2Te3)12 superlattice‐like films, leading to much improved thermoelectric power factors (PFs). The (MnTe)0.1(Sb2Te3)12 obtains the highest room‐temperature PF of 2.50 mWm−1K−2, while the (MnTe)0.25(Sb2Te3)12 possesses the highest PF of 2.79 mWm−1K−2 at 381 K, remarkably superior to the values acquired in binary MnTe and Sb2Te3 films. This research provides valuable guidance on understanding and rationally tailoring the interfacial charge transfer of thermoelectric SLs to further enhance thermoelectric performances.

A [formula omitted] drift velocity monitoring chamber for the MEG II experiment

The MEG-II experiment searches for the lepton-flavor-violating decay: μ⟶e+γ. The reconstruction of the positron trajectory uses a drift chamber operated with a mixture of He and iC4H10 gas. It is crucial to provide a stable performance of the detector in terms of its electron transport parameters, avalanche multiplication, composition and purity of the gas mixture. In order to have a continuous monitoring of the quality of the gas injected, we plan to install a small drift chamber, with a simple geometry that allows to measure very precisely the electron drift velocity in a prompt way. The chamber is a small box with cathode walls, that determine a highly uniform electric field inside two adjacent drift cells. Along the axis separating the two drift cells, four staggered sense wires alternated with five guard wires collect the drifting electrons. The trigger is provided by two 90Sr radioactive sources placed on top of a two thin scintillator tiles telescope. The whole system is designed to give a response in few minutes about drift velocity variations at the 10−3 level. In this paper the development of the drift chamber is presented, with a particular focus on the details of its construction.

Increased sedoheptulose-1,7-bisphosphatase content in Setaria viridis does not affect C4 photosynthesis.

Sedoheptulose-1,7-bisphosphatase (SBPase) is one of the rate-limiting enzymes of the Calvin cycle, and increasing the abundance of SBPase in C3 plants provides higher photosynthetic rates and stimulates biomass and yield. C4 plants usually have higher photosynthetic rates because they operate a biochemical CO2-concentrating mechanism between mesophyll and bundle sheath cells. In the C4 system, SBPase and other enzymes of the Calvin cycle are localized to the bundle sheath cells. Here we tested what effect increasing abundance of SBPase would have on C4 photosynthesis. Using green foxtail millet (Setaria viridis), a model C4 plant of NADP-ME subtype, we created transgenic plants with 1.5 to 3.2 times higher SBPase content compared to wild-type plants. Transcripts of the transgene were found predominantly in the bundle sheaths suggesting the correct cellular localization of the protein. The abundance of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit was not affected in transgenic plants overexpressing SBPase, and neither was leaf chlorophyll content or photosynthetic electron transport parameters. We found no association between SBPase content in S. viridis and saturating rates of CO2 assimilation. Moreover, a detailed analysis of CO2 assimilation rates at different CO2 partial pressures, irradiances, and leaf temperatures showed no improvement of photosynthesis in plants overexpressing SBPase. We discuss the potential implications of these results for understanding the role of SBPase in regulation of C4 photosynthesis.

Space-charge domains in n-type GaN epilayers under pulsed electric field

Formation and drift of space-charge domains with velocity of sound were experimentally observed in charge current traces of a high-quality lightly doped GaN semiconductor under pulsed electric fields at room and liquid nitrogen temperatures. A GaN epilayer was developed on an Ammono GaN substrate to achieve the electron density and low-field mobility values of 1.06 × 1016 cm−3 and 1021 cm2/V s (at 300 K) and 0.21 × 1016 cm−3 and 2652 cm2/V s (at 77 K), respectively. The formation of moving space-charge domains was observed only in samples with the lengths of 1 mm and longer arising at the critical electric fields starting from ∼0.4 and ∼0.8 kV/cm at 77 and 300 K, respectively. Basic electron transport parameters were found investigating short samples with the lengths of 65 μm and shorter in a wide range of electric fields up to 150 kV/cm, at which the thermal material breakdown occurred. The critical length of a sample for space-charge domain formation was estimated considering the acoustoelectric effects in analysis of pulsed current–voltage characteristics, thus defining the constraints for the design of GaN-based power electronic devices.