Electron Charging Research Articles

Compressing Double [7]Helicene by Successive Charging with Electrons.

Chemical reduction of a benzo-fused double [7]helicene (1) with two alkali metals, K and Rb, provided access to three different reduced states of 1. The doubly-reduced helicene 12- has been characterized by single-crystal X-ray diffraction as a solvent-separated ion triplet with two potassium counterions. The triply- and tetra-reduced helicenes, 13- and 14- , have been crystallized together in an equimolar ratio and both form the contact-ion complexes with two Rb+ ions each, leaving three remaining Rb+ ions wrapped by crown ether and THF molecules. As structural consequence of the stepwise reduction of 1, the central axis of helicene becomes more compressed upon electron addition (1.42 Å in 14- vs. 2.09 Å in 1). This is accompanied by an extra core twist, as the peripheral dihedral angle increases from 16.5° in 1 to 20.7° in 14- . Theoretical calculations provided the pattern of negative charge build-up and distribution over the contorted helicene framework upon each electron addition, and the results are consistent with the X-ray crystallographic and NMR spectroscopic data.

Effect of B-doping on photoluminescence properties of Si quantum dots with Ge core

Boron-doped Ge-core/Si-shell quantum dots (Si-QDs with Ge core) were self-assembled on thermally-grown SiO2 from the thermal decomposition of alternate pure SiH4 and GeH4 diluted with H2. Changes in the surface potential caused by electron charging to the B-doped Si-QD with Ge core were studied using a Kelvin probe technique in atomic force microscopy. We also demonstrated that the room temperature photoluminescence (PL) intensity increased appreciably with B-doping into the Si shell. The increase in the PL intensity is interpreted in terms of a hole(s) in the Ge core and a negatively-charged ionized B acceptor(s) in the Si shell resulting from electron transfer from the valence band of the Ge core to the B acceptor, which increased the amplitude of the electron wave function penetrating the Ge core from the Si shell to enhance the radiative recombination rate between electrons in the conduction band and holes in the valence band of the Ge core.

Resistance drift in Ge2Sb2Te5 phase change memory line cells at low temperatures and its response to photoexcitation

Resistance drift in amorphous Ge2Sb2Te5 is experimentally characterized in melt-quenched line cells in the range of 300 K to 125 K and is observed to follow the previously reported power-law behavior with drift coefficients in the range of 0.07 to 0.11 in the dark, linearly decreasing with 1/kT. While these drift coefficients measured in the dark are similar to commonly observed drift coefficients (∼0.1) at and above room temperature, measurements under light show a significantly lower drift coefficient (0.05 under illumination vs 0.09 in the dark at 150 K). Periodic on/off switching of light shows a sudden decrease/increase in resistance, attributed to photo-excited carriers, followed by a very slow response (∼30 min at 150 K) attributed to contribution of electron traps and slow trap-to-trap charge exchanges. A device-level electronic model is used to relate these experimental findings to gradual charging of electron traps in amorphous Ge2Sb2Te5, which gives rise to growth of a potential barrier for holes in time and, hence, resistance drift.

Two-Dimensional Nature and the Meaning of the Density of States in Redox Monolayers

It has been suggested that the transport of charge in molecular electronics and redox junctions are, at the sub-nanoscale, i.e. for dimensions lower than 5 nm, fundamentally related [\textit{Phys. ...

Doping of Fe on room-temperature-synthesized CoNi layered double hydroxide as an excellent bifunctional catalyst in alkaline media

Currently, the high demand for energy results in a large amount of pollution, which is of great concern. To overcome this problem, a highly active and low-cost bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial to satisfy industrial criteria. Layered double hydroxides (LDH) attracted significant interest in several fields, including catalysis, storage of energy, delivery of druges, etc. A simple coprecipitation method for the preparation of highly active electrochemical Fex/CoNi LDH catalysts at room temperature was described here. In alkaline media, from series of prepared catalysts, the Fe8%/Co–Ni LDH shows superior electrocatalytic activity with an overpotential of 232 mV at 10 mA/cm2, and Eo 91 V and E1/2 0.83 V versus RHE comparable to both noble metal-based and noble-metal-free OER/ORR catalysts recorded. Proper electronic structure and charging resistance that can facilitate the reduction of electron movement in the ORR/OER, are considered as two main factors in reducing the over-potential catalytic reaction.

Tracking with wakefields in dielectric laser acceleration grating structures

Due to the tiny apertures of dielectric laser acceleration grating structures within the range of the optical wavelength, wakefields limit the bunch charge for relativistic electrons to a few femtocoulomb. In this paper, we present a wakefield upgrade of our six-dimensional tracking scheme DLAtrack6D in order to analyze these limitations. Simulations with CST Studio Suite provide the wake functions to calculate the kicks within each tracking step. Scaling laws and the dependency of the wake on geometrical changes are calculated. The tracking with wakefields is applied to beam and structure parameters following recently performed and planned experiments. We compare the results to analytical models and identify intensity limits due to the transverse beam breakup and strong head-tail instability. Furthermore, we reconstruct phase advance spectrograms and use them to analyze possible stabilization mechanisms.

Fabrication of Fe-Ni Ultrafine Particles Epoxy Composite Film Using the LbL Assisted Composite Plating Method

Magnetic ultrafine particles-insulator composite films including Fe-Ni ultrafine particles and insulating epoxy films used for electromagnetic wave absorbing films were synthesized by a newly developed electrochemical method termed the “LbL assisted composite plating method”.The reaction solution containing 40 ml / L water-solve epoxy resin prepared by NIPPON PAINT Co., LTD and 0-3 g / L Fe-Ni ultrafine particles 60 nm in diameter manufactured by the Nilaco corporation were used for film fabrication. Cu substrates and Ti / Pt plates were used as the cathode and anode, respectively.Epoxy films were deposited by the following schemes:O2 + 2H2O +4e- → 4OH- (Resin)3NH+ + OH- → (Resin)3N + H2OIn LbL assisted composite plating, charged Fe-Ni ultrafine particles are attracted to the cathode by electrostatic force simultaneously with insulator epoxy film electrodeposition. LbL treatment was performed using 1 wt.% PSS (Poly (sodium 4-styrenesulfonate)) and 0.5 mM NaCl solution, and 1 wt.% PDDA (poly (diallyl dimethyl ammonium chloride)) and 0.5 mM NaCl solution. Fe-Ni ultrafine particles were alternately immersed in PSS solution and PDDA solution.In water Fe-Ni ultrafine particles before LbL treatment have 20 mV zeta potential. After immersion in PSS solution, Fe-Ni ultrafine particles have -40 mV zeta potential, and after immersion in PDDA solution, Fe-Ni zeta potential increases to 60 mV. This increase of zeta potential means that the amount of charged electrons on the ultrafine particles surface were increased through a layer by layer structure of cationic and anionic polyelectrolytes formed on the particles. The Fe-Ni ultrafine particles not treated with LbL precipitated in the reaction solution within 30 minutes, while the particles subjected to the LbL treatment were stable in the reaction solution over 16 days. Figure 1 shows the particle size distribution of Fe-Ni ultrafine particles with LbL treatment and without LbL treatment in water. The peak diameters of the distribution curves with LbL treatment and without LbL treatment were 35 nm and 52 nm, respectively. LbL treatment using PSS and PDDA were effective for increasing the charging electrons on Fe-Ni ultrafine particles and for enhancing the dispersibility of ultrafine particles in the reaction solution.At electrophoresis of only Fe-Ni ultrafine particles without epoxy film on Cu substrate, the 4.3-fold increase in the mass of deposited particles with LbL treatment was observed compared with no LbL treatment, as a result of the increase of charging electrons on Fe-Ni particles.Electrodeposition of Fe-Ni ultrafine particle-epoxy composite films was conducted under a constant current density of 4 mA / cm2, and 5-minute deposition time using the LbL assisted composite plating method. The film thickness was measured from the cross-section SEM image of the films. The film thickness of the deposited film prepared from the reaction solution containing 3 g / L Fe-Ni fine particles without LbL treatment is about 30μm, whereas that prepared from the reaction solution containing 3 g / L Fe-Ni particles with LbL treatment is about 80 μm. From the EDX mapping image of the film prepared using Fe-Ni particles without LbL treatment, the agglomerates of Fe-Ni particles were observed. On the other hand, there are no agglomerates in the film prepared using Fe-Ni particles with LbL treatment.These aggregates of Fe-Ni particles not treated with LbL were generated due to less electron charging on the particle surface than particles having LbL treatment, and act as the growth inhibiter of the epoxy film. Therefore, the film thickness of the films prepared using Fe-Ni particles not treated with LbL was less than that of the film prepared using Fe-Ni particles having LbL treatment.Figure 2 shows the Fe-Ni content in the films dependence on the concentration of Fe-Ni ultrafine particles in the reaction solution. The Fe-Ni content in the films increased in proportion to the Fe-Ni concentration in the reaction solution. Using LbL treatment, the Fe-Ni content in the films increased 1.6 times compared to that without LbL treatment. Over 22 vol. % Fe-Ni ultrafine particles included in epoxy films were successfully obtained using LbL assisted composite plating from the 3 g / L Fe-Ni content reaction solution.The experimental results clearly show the dispersibility in the reaction solution could be greatly improved using LbL treatment for Fe-Ni ultrafine particles, and Fe-Ni ultrafine particles uniformly dispersed in epoxy film could be fabricated using our newly developed electrochemical method. Figure 1

500 microkelvin nanoelectronics.

Fragile quantum effects such as single electron charging in quantum dots or macroscopic coherent tunneling in superconducting junctions are the basis of modern quantum technologies. These phenomena can only be observed in devices where the characteristic spacing between energy levels exceeds the thermal energy, kBT, demanding effective refrigeration techniques for nanoscale electronic devices. Commercially available dilution refrigerators have enabled typical electron temperatures in the 10 to 100 mK regime, however indirect cooling of nanodevices becomes inefficient due to stray radiofrequency heating and weak thermal coupling of electrons to the device substrate. Here, we report on passing the millikelvin barrier for a nanoelectronic device. Using a combination of on-chip and off-chip nuclear refrigeration, we reach an ultimate electron temperature of Te = 421 ± 35 μK and a hold time exceeding 85 h below 700 μK measured by a self-calibrated Coulomb-blockade thermometer.

Conductivity tuning of charged triazine and heptazine graphitic carbon nitride (g-C3N4) quantum dots via nonmetal (B, O, S, P) doping: DFT calculations

Chemical doping of graphitic carbon nitride (g-C3N4) quantum dots with nontoxic heteroatoms has proven to be an effective means for tuning the electrical properties of this two-dimensional (2D) nanomaterial. In this investigation, triazine (tg-CN) and heptazine (hg-CN) clusters were doped with the p-block (B, O, S, and P) elements, and were further compared in terms of siting and conductance using density functional theory (DFT) at the HSE06/6-311+G* level. The calculation results predicted that B doping in both types of g-C3N4 was favored in place of carbon atoms while the O, S, and P dopants preferred nitrogen atoms, where P siting was dependent on the type of material. Both the initial HOMO–LUMO gap and global hardness were decreased after the substitution, with the most substantial changes after the O and S doping in the hg-CN and tg-CN structures, respectively. The HOMO–LUMO gap changed most significantly (by up to 3.79 eV) with the [+/−] charge switching for the O-doped nanocluster. In contrast to hg-CN, tg-CN turned from an insulator into metallic or half-metallic material upon electron charging. Finally, both hg-CN and tg-CN became better electrophiles after modification, particularly with B doping.

A Study on Biological Sample Preparation for High Resolution Imaging of Scanning Electron Microscope

Green chemistry has drawn attention for synthesizing nanoparticles as it utilizes an eco-friendly nontoxic chemical in the synthesis protocol. In addition, researchers start looking into the potential of organism such as bacteria, fungi and plants for synthesizing nanoparticles. Synthesis of nanoparticles requires details on structural analysis before/after synthesis in order to evaluate and control the quality of nanoparticles. Scanning electron microscope (SEM) has been widely used as an imaging instrument to structurally characterize nanoparticles before/after synthesis process. Maintaining the vacuum level in SEM system and controlling contamination originated from the sample are crucially important to enable high resolution imaging. In addition, sample surface need to be conductive to prevent image distortion due to the electron charging effect. Hence, raise the importance to study the method in preparing biological sample for SEM imaging. This work focuses on the three approaches of drying process for plant, bacteria and algae samples. Proper selection of preparation method on each samples involving air-drying using HMDS, CPD and FD methods have been done in order to prevent surface tension effect during drying process, which will result in the modification of the original structure. Comparison was made to get insight on the suitable sample preparation method for the specific biological sample. It is found that air-drying or CPD methods are suitable for the liquid-rich biological sample, while FD method can be a preference for biological sample that contains less liquid.

Energy recovery in capacitive deionization systems with inverted operation characteristics

Capacitive deionization (CDI) operated under inverted mode involves electronic charging and discharge steps with corresponding ion concentration and desalting coupled with simultaneous energy storage.

Electrostatic charging and precipitation of nanoparticles in technical nitrogen: Highly efficient diffusion charging by hot free electrons

Electrostatic charging and deposition of a liquid nano-aerosol was studied in dry air and in technical (3.6 % O2) nitrogen. The experiments have shown that electronic charging of aerosols can be important in technical scale electrostatic precipitators (ESPs). Already at operation voltages just slightly above the corona onset voltage, the contribution of the free electrons to the overall current is estimated to be around 50 %. Due to the high temperature of free electrons, diffusion charging by free electrons allows to reach exceptionally high particle charge and extremely high precipitation efficiency.A strongly simplified theoretical model was developed, which gives a good prediction of particle charge based on averaged values of particle diameter, current density, electric field strength, electron temperature and residence time. The ion mobilities were determined by fitting the current-voltage characteristics with a modified Townsend (Monrolin et al. 2018) equation and are significantly higher than the values typically used to describe diffusion charging in air. This may be ascribed to the very dry gas phase and the short average lifespan of the ions under ESP conditions, which is in the order of 1 ms.From the practical point of view, electronic charging might be relevant in a number of technical applications, including high temperature ESPs, ESP applications in dry and oxygen-free gases and pulsed corona systems.

Mutual control of coherent spin waves and magnetic domain walls in a magnonic device.

The successful implementation of spin-wave devices requires efficient modulation of spin-wave propagation. Using cobalt/nickel multilayer films, we experimentally demonstrate that nanometer-wide magnetic domain walls can be applied to manipulate the phase and magnitude of coherent spin waves in a nonvolatile manner. We further show that a spin wave can, in turn, be used to change the position of magnetic domain walls by means of the spin-transfer torque effect generated from magnon spin current. This mutual interaction between spin waves and magnetic domain walls opens up the possibility of realizing all-magnon spintronic devices, in which one spin-wave signal can be used to control others by reconfiguring magnetic domain structures.

Toward magnonic devices

Magnonics The field of magnonics aims to use spin waves (SWs) and their associated quasiparticles—magnons—as carriers of information. Compared with the movement of charge in conventional electronics, a major advantage of SWs is reduced Joule heating. However, SWs are trickier to direct and control. Two groups now go a step further toward magnon-based devices. Han et al. show that in multilayer films, domain walls can be used to change the phase and magnitude of a spin wave. Wang et al. demonstrate how magnon currents can be used to switch the magnetization of an adjacent layer. Science , this issue p. [1121][1], p. [1125][2] [1]: /lookup/doi/10.1126/science.aau2610 [2]: /lookup/doi/10.1126/science.aav8076

Evaluating a Self-Charging Electrostatic Dust Shield for Solar Cell applications in Baghdad Outdoor Weather

Introduction: It is well known that the biggest problem facing the utilizing of solar cell Panels in Baghdad is the unpredictable dusty weather through the days of year. This big problem is not easy to overcome due to the frequent dust accumulations and the high cost of cleaning and other maintenance problems. Dust problems are increasing due to global warming. In Baghdad city, where solar radiation is intense and available almost throughout the year, Deposition of dust on the panels could severely minimize solar-to power output efficiency. There are many methods for dust removing from surfaces like the natural dust removal of wind, mechanical dust removing, super-hydrophobic on solar panel surface, and the electrostatic method which is adopted in this work. The dust particles will be charged statistically by rolling on the surface of the solar panels they will have the same electric charge and the electrostatic forces between them are repulsion. Hence, the dust particles will float away from the solar panels. Materials and Methods: A self-charging transparent conductive glass is prepared by spraying a thin film (141 nm thickness) of a Tin dioxide (SnO2) solution on a glass substrate (12x12 cm2). The dust shield is connected to an electronic charging circuit. The shield is located on the top of a silicon solar cell. The novel idea is that the shield is electrically supplied by the solar cell itself whereas D.C. current from the solar cell itself is used to charge the conductive glass, which is located on the top surface of the cell. Results and Discussion: A test was done for dust removing from a Silicon solar cell by electrostatic repulsion method, considering matching the spectral response region of the Siliconsolar cells with the film transmittance spectral region (400 -700 nm). The transmittance value is between (92 – 95)% and results are compared withan identical reference solar cell. Results show a good response as the calculated clearing factor value increases due to the cell efficiency increment.Also, the clearing factor is discussed as a function of outdoor temperature to show a direct proportionality, while the environmental humidity showed an inverse proportionality. Conclusions: A self-cleaning method for a solar cell is successfully introduced via a conductive glass. tests were carried outdoor in Baghdad city. Results showed that there is a direct proportionality between both: the clearing factor and the efficiency gain with the ambient temperature. The ambient humidity showed indirect proportionality with system efficiency (clearing factor and efficiency gain show reduction as the humidity percentage increases).

UV or blue light excited red persistent perovskite phosphor with millisecond lifetime for use in AC-LEDs.

Energy storage phosphors with millisecond period afterglow that compensate for the diming time of alternating current light-emitting diodes (AC-LEDs) have promising application. To obtain a persistent luminescence (PersL) white colour in AC-LEDs, we focussed on a red afterglow with short period phosphorescence. Ca4 Ti3 O10 forms a type of perovskite-related Ruddlesden-Popper phase structure. Doping Pr3+ ions into Ca4 Ti3 O10 , an ideal red PersL was obtained. X-ray diffraction and element analysis demonstrated that our target samples were crystallized well. Steady-state and afterglow luminescence properties were investigated in detail. Notably, the PersL intensity was dependent on various excitation wavelengths. By measuring three-dimensional thermoluminescence spectra, we found that the trap depths showed a continuous distribution and that the shallowest trap contributed to the millisecond afterglow. Two PersL mechanism models were used to elucidate the electron charging and de-trapping processes under UV or blue light activation.

Measurement of electric fields of charged spray clouds of conductive liquids in free space and in a conductive vessel

The process of spraying liquids generated electrical charges. The question therefore arises as to whether this electrostatic charge represent an ignition hazard when an explosive mixture is present. This hazard occurs when cleaning vessels, in which an explosive mixture is formed by residues of easily flammable liquids or the cleaning medium itself. Although measurement techniques and methods exist for detecting this electrostatic charging process, they have not been sufficiently scientifically proven. The Chilworth JCI 131 adverse conditions field meter is to be used to measure the electrostatic charging of sprayed liquids. It shall be validated by measuring the electric field strength of a flat spray water jet in low-pressure range (8 bar) charged by contact charging and accumulation of free electrons of a commercial, insulated arranged electrostatic spraying system (up to - 90 kV). A flat-jet nozzle is selected which atomizes the spray jet, which serves as the measuring surface, sufficiently large. This arrangement is further investigated in a 1 m3 stainless steel IBC. The investigations presented are part of a project aiming to extend the scope of the German Technical Rules for Hazardous Substances (TRGS) of TRGS 727, which regulate avoiding ignition hazards resulting from electrostatic charging. The aim is to reach an understanding that allows provisions for safe cleaning of “small” and “medium-sized” containers up to 50 m3. This project is funded by DGUV (German Social Accident Insurance) and partners from the industry.

Analysis of the detection response of waveguide-integrated superconducting nanowire single-photon detectors at high count rate

Nanophotonic circuitry and superconducting nanowires have been successfully combined for detecting single photons, propagating in an integrated photonic circuit, with high efficiency and low noise and timing uncertainty. Waveguide-integrated superconducting nanowire single-photon detectors (SNSPDs) can nowadays be engineered to achieve subnanosecond recovery times and can potentially be adopted for applications requiring Gcps count rates. However, particular attention shall be paid to such an extreme count rate regime since artifacts in the detector functionality emerge. In particular, a count-rate dependent detection efficiency has been encountered that can compromise the accuracy of quantum detector tomography experiments. Here, we investigate the response of waveguide-integrated SNSPDs at high photon flux and identify the presence of parasitic currents due to the accumulation of charge in the readout electronics to cause the above-mentioned artifact in the detection efficiency. Our approach allows us to determine the maximum photon count rate at which the detector can be operated without adverse effects. Our findings are particularly important to avoid artifacts when applying SNSPDs for quantum tomography.

Resolution enhancement in scanning electron microscopy using deep learning

We report resolution enhancement in scanning electron microscopy (SEM) images using a generative adversarial network. We demonstrate the veracity of this deep learning-based super-resolution technique by inferring unresolved features in low-resolution SEM images and comparing them with the accurately co-registered high-resolution SEM images of the same samples. Through spatial frequency analysis, we also report that our method generates images with frequency spectra matching higher resolution SEM images of the same fields-of-view. By using this technique, higher resolution SEM images can be taken faster, while also reducing both electron charging and damage to the samples.

Disentangling Highly Asymmetric Magnetoelectric Effects in Engineered Multiferroic Heterostructures

One of the main strategies to control magnetism by voltage is the use of magnetostrictive-piezoelectric hybrid materials, such as ferromagnetic-ferroelectric heterostructures. When such heterostructures are subjected to an electric field, piezostrain-mediated effects, electronic charging, and voltage-driven oxygen migration (magnetoionics) may simultaneously occur, making the interpretation of the magnetoelectric effects not straightforward and often leading to misconceptions. Typically, the strain-mediated magnetoelectric response is symmetric with respect to the sign of the applied voltage because the induced strain (and variations in the magnetization) depends on the square of the ferroelectric polarization. Conversely, asymmetric responses can be obtained from electronic charging and voltage-driven oxygen migration. By engineering a ferromagnetic-ferroelectric hybrid consisting of a magnetically soft 50-nm thick Fe75Al25 (at. %) thin film on top of a (110)-oriented Pb(Mg1/3Nb2/3)O3-32PbTiO3 ferroelectric crystal, a highly asymmetric magnetoelectric response is obtained and the aforementioned magnetoelectric effects can be disentangled. Specifically, the large thickness of the Fe75Al25 layer allows dismissing any possible charge accumulation effect, whereas no evidence of magnetoionics is observed experimentally, as expected from the high resistance to oxidation of Fe75Al25, leaving strain as the only mechanism to modulate the asymmetric magnetoelectric response. The origin of this asymmetric strain-induced magnetoelectric effect arises from the asymmetry of the polarization reversal in the particular crystallographic orientation of the ferroelectric substrate. These results are important to optimize the performance of artificial multiferroic heterostructures.