Schottky Field Research Articles

Electric Field Features and Charge Behavior in Oil-Pressboard Composite Insulation under Impulse Voltage

Oil-pressboard/paper insulation materials are essential in transformers for ensuring their safe and stable operation, primarily due to their roles in spatial electric field distribution and charge migration mechanisms. Current spatial distribution analyses rely on computational methods that lack empirical validation, particularly for oil-pressboard/paper composites. This study leverages the principles of the Kerr electro-optic effect to develop a rapid measurement platform for electric fields within oil-pressboard/paper insulation under impulse voltage conditions, which measures the spatial electric field characteristics using Cu-Cu and Al-Al electrodes under various scenarios: with asymmetric and symmetric pressboard coverage and different numbers of insulating paper layers. Findings indicated: (1) In asymmetric pressboard models, Cu-Cu electrodes exhibit a consistent peak electric field of approximately 16 kV/mm, while Al-Al electrodes show peak values of 18.13 kV/mm and −14.98 kV/mm. Charge density patterns are similar, with Cu-Cu at about 68 μC/m2 and Al-Al at 11.2 μC/m2 and −124.8 μC/m2. (2) Symmetric models present consistent peak electric fields and charge densities for both polarities. (3) Increasing insulating paper layers elevates electric field strengths. Both electrodes show the similar peak field of about 17 kV/mm with differing paper layers due to higher charge injection from the Al electrode. (4) Utilizing the Schottky effect and field emission principles, the study clarifies charge generation and migration mechanisms. These insights could provide a theoretical foundation for designing and verifying oil-pressboard/paper insulation structures in transformers.

Precise measurement of spatial coherence and axial brightness based on the Wigner function reconstruction in transmission electron microscopes with field emission guns and a thermionic emission gun.

The spatial coherence and the axial brightness of a cold field emission gun, a Schottky field emission gun and a $\mathrm{LaB}_6$ thermionic gun are precisely measured. By analyzing the Airy pattern from a selected area aperture, various parameters including the spatial coherence length are determined. Using the determined coherence length, the axial brightness of the field emission guns is estimated using the equation which we previously derived based on the discussion of the Wigner function of an electron beam. We also make some extensions in the method to be applicable to the measurements of the thermionic gun, which has anisotropic intensity distribution in most case unlike the field emission guns. Not conventional average brightness but the axial brightness measured for the three kinds of emitters are compared accurately and precisely without influenced by the measurement conditions.

Utilizing the synergistic effect between the Schottky barrier and field redistribution to achieve high-density, low-consumption, cellulose-based flexible dielectric films for next-generation green energy storage capacitors

Due to the synergistic effect of field redistribution and the Fermi level's moving, an ESD of 31.07 J cm−3 with η of 80.03% was obtained in the SZS, which is the best performance in cellulose-based dielectric capacitors to the authors' knowledge.

Chitosan-Reinforced Gelatin Microspheres-Modified Glass Ionomer Cement (GIC): A Novel Bone Alloplast Graft Material Synthesis and an In Vivo Analysis.

Aim and objective The study aimed to assess and evaluate the efficacyof glass ionomer modified with chitosan-reinforced gelatin microspheres on bone formation. Materials and methods The study involved three groups: Group I comprised plain glass ionomer cement; Group II comprised glass ionomer cement/gelatin (70:30 wt%); in Group III, glass ionomer cement/gelatin/chitosan (70:30%) scaffold were made into discs; the gelatin microspheres were synthesized by oil emulsion method. The synthesized scaffold was subjected to the following in vitro testing, Instron Universal Testing Machine (UTM), U3000, (Instron Corporation, Norwood, Massachusetts, United States) to assess compressive strength, scanning electron microscope(SEM) examination, and biocompatibility testing using hemocompatibility assay. The material was then testedin vivo; male Wistar albino rats, a total of nine animals, were utilized for this purpose. Three animals were used in each group; a femoral defect model was the model of choice for the experiment and the animals were observed for a period of four weeks, following which the animals were sacrificed and sent for histopathological analysis. Results The compression testing was carried out using UTM; test group I was 33 MPa, test group II was 2.3 MPa, and test group III was 25.75 MPa. SEM (JSM-IT800 Schottky Field Emission NANO SEM (JEOL, Tokyo, Japan)) analysis was done to observe the porosity of the fabricated scaffold with the average measurement of0.12 ± 0.2 μm in test group II and 0.29 ± 0.4μm in test group III. Hemocompatibility reports noted 0.4-0.8% lysis for the synthesized scaffolds. Histopathology staining of the femur defects showed that group III favoured bone formation. One-way analysis of variance (ANOVA) and post hoc Bonferroni test was done on the data. The optical density values of the alizarin red stained slide showed statistical significance for group III. Conclusion In conclusion, the synthesized scaffolds are biocompatible, distribution of porosity andpore characteristics in the glass ionomer cement/gelatin/chitosan group is better than that of the glass ionomer cement/gelatin group. The glass ionomer cement/gelatin/chitosan group had better compressive strength and induced more bone formation compared to the other test group and the control. Thus, the novel glass ionomer modified with chitosan-reinforced gelatin microspheres has optimal properties to be used as a bone graft material.

Looking Outside the Square: The Growth, Structure, and Resilient Two-Dimensional Surface Electron Gas of Square SnO2 Nanotubes.

Nanotechnology has delivered an amazing range of new materials such as nanowires, tubes, ribbons, belts, cages, flowers, and sheets. However, these are usually circular, cylindrical, or hexagonal in nature, while nanostructures with square geometries are comparatively rare. Here, a highly scalable method is reported for producing vertically aligned Sb-doped SnO2 nanotubes with perfectly-square geometries on Au nanoparticle covered m-plane sapphire using mist chemical vapor deposition. Their inclination can be varied using r- and a-plane sapphire, while unaligned square nanotubes of the same high structural quality can be grown on silicon and quartz. X-ray diffraction measurements and transmission electron microscopy show that they adopt the rutile structure growing in the [001] direction with (110) sidewalls, while synchrotron X-ray photoelectron spectroscopy reveals the presence of an unusually strong and thermally resilient 2D surface electron gas. This is created by donor-like states produced by the hydroxylation of the surface and is sustained at temperatures above 400°C by the formation of in-plane oxygen vacancies. This persistent high surface electron density is expected to prove useful in gas sensing and catalytic applications of these remarkable structures. To illustrate their device potential, square SnO2 nanotube Schottky diodes and field effect transistors with excellent performance characteristics are fabricated.

In multi electron beam systems, “Neighbours Matter”

In the Multi beam source (MBS) of our Multi Beam Scanning Electron Microscope (MBSEM), an aperture lens array (ALA) splits the emission cone of the Schottky field emitter into multiple beamlets. When the apertures in the ALA are close to each other, the ALA can introduce aberrations to these beamlets through the electrostatic interaction of neighbouring apertures with each aperture's lens field. When the apertures are arranged in a square grid pattern, the aberration causes fourfold astigmatism. The effect on the beam spot is analyzed through a combination of 3D simulations and experimental validation. To counterbalance the fourfold astigmatism, a correction scheme is proposed in which a slightly non-round profile is applied to the aperture lenses.

EFFECTS OF PROFESSIONAL ORAL HYGIENE AND TEETH WHITENING ON THE MICROELEMENT COMPOSITION OF ENAMEL

Aim: The objective of this study is to investigate the impact of professional teeth cleaning and the substances used in modern dentistry for whitening on the microelement composition of tooth enamel. Materials and Methods: To study the morphology and microelement composition of the enamel, scanning electron microscopy was performed using the MiraLM microscope equipped with a Schottky field emission electron gun from Tescan. Results: A comparative analysis between the areas subjected to mechanical cleaning and those where it was not applied revealed a significant difference in the research results, particularly in carbon, which changed from 25.16±1.04 to 32.02±1.8. An analysis of the enamel’s chemical composition before and after whitening revealed a decrease in carbon from 45.91±1.20 to 42.46±1.74. The change in phosphorus content was determined to be from 9.77±0.39 to 9.56±0.75. A decrease in calcium from 15.96±0.64 to 15.21±1.22 and magnesium from 0.07±0.01 to 0.01±0.01 was also observed. Conclusions: Professional dental hygiene does not have a direct impact on the microelement composition of enamel, such as the levels of calcium, phosphorus, fluoride, and other microelements. However, it can have an indirect and temporary influence due to the use of abrasive materials that affect dental deposits, pellicle, and the surface layer of enamel. Teeth whitening can affect the microelement composition of enamel, but these changes are mostly temporary and associated with processes of demineralization/ remineralization and oxygenation.

Effect of overlap region for schottky metal and field oxide on the electrical characteristics of 6500 V/50A 4H-SiC JBS diodes

The effect of overlap region for schottky metal and field oxide (ORSMFO) of field limiting rings termination on the reverse breakdown voltage of 6500 V/50A 4H-SiC JBS diodes was studied. Two comparative diodes were designed and fabricated. The reverse breakdown voltage of diodes with 20 μm ORSMFO improved significantly, which was up to 7000 V at the reverse leakage current of 10 μA and yield was up to 73 %. The structure simulation implied that the difference of the ORSMFO influenced the electric field strongly. Compared with the simulative terminal structure with 3 μm and 0 μm ORSMFO, the electric field intensity of the simulative terminal structure with 20 μm ORSMFO reduced by about 30 %-50 % near the main junction and the first three field rings.

Recent Progress on Sensitivity Analysis of Schottky Field Effect transistor Based Biosensors

In this review, we explored the modern development of schottky field effect transistor (SK FET) structures and the improvement of sensitivity of nanowire sensors using dielectric modulation. Here, the recent developments compared with the conventional schottky FET sensor, and modified conventional configuration have improved sensitivity and faster responses controlled by dielectric modulation and changing the barrier height. The change in sensitivity- with the current optimization has been considered for dissimilar gate, and drain voltage. The dielectric modulation can advance the finding limits, sensitivity, and reaction time of the novel structures in dissimilar applications, such as U-V finding, gas and chemical/ biosensing. In addition, the efficiency and doped channel have been deliberately studied under dissimilar biomolecule model specifications. This article reviews a recent study on emerging future generation SK FET biosensors with their sensitivity performance and the effect of their metal and channel contact is presented.

What ails the photovoltaic performance in single-layered unpoled BFO? – The role of oxygen annealing in improving the photovoltaic efficiency

We report enhanced photovoltaic efficiency in optimized monolayer BiFeO3 (BFO) thin-film based solar cells prepared by inexpensive spin-coating technique. The short circuit current density and open-circuit voltage of the single-layer BFO cell were measured to be 1.91 mA/cm2 and 0.92 V, respectively, which is much higher than the reported values so far in monolayer BFO based photovoltaic systems. The influence of oxygen annealing on photovoltaic response is investigated, and a further improvement in photo-current density is reported. The phase purity and average crystallite size are examined by X-ray diffraction studies, which confirmed the single-phase formation of rhombohedrally distorted perovskite BFO structured layer deposition. The average crystallite size, as determined by the Williamson-Hall method, is found to be in the range of 14 – 17 nm. The micrographs reveal a uniform and crack-free deposition of both the thin-films. The cross-sectional images reveal the smooth film deposition of thicknesses in the range of 360 – 370 nm. The average bandgap values of the air and oxygen annealed films are found to be 2.57±0.02 eV and 2.64 ± 0.02 eV, respectively. The oxygen annealing of these films show a significant reduction in Urbach energy tail values from 0.37 ± 0.02 eV to 0.28 ± 0.03 eV, which suggests a lower density of defect states in the oxygenated films. The X-ray photoelectron analysis showed a noticeable reduction in Fe2+ ions, hence supporting the Urbach energy studies. We also demonstrate a metal–semiconductor-metal model to explain the enhancement in short-circuit current density, suggesting that the main driving force for the photo-generated charge carriers is the Schottky field at the interfaces rather than the inherent polarization field in the as-deposited (unpolled) BFO films.

Exploring high-resolution cryo-ET and subtomogram averaging capabilities of contemporary DEDs

The potential of energy filtering and direct electron detection for cryo-electron microscopy (cryo-EM) has been well documented. Here, we assess the performance of recently introduced hardware for cryo-electron tomography (cryo-ET) and subtomogram averaging (STA), an increasingly popular structural determination method for complex 3D specimens. We acquired cryo-ET datasets of EIAV virus-like particles (VLPs) on two contemporary cryo-EM systems equipped with different energy filters and direct electron detectors (DED), specifically a Krios G4, equipped with a cold field emission gun (CFEG), Thermo Fisher Scientific Selectris X energy filter, and a Falcon 4 DED; and a Krios G3i, with a Schottky field emission gun (XFEG), a Gatan Bioquantum energy filter, and a K3 DED. We performed constrained cross-correlation-based STA on equally sized datasets acquired on the respective systems. The resulting EIAV CA hexamer reconstructions show that both systems perform comparably in the 4–6 Å resolution range based on Fourier-Shell correlation (FSC). In addition, by employing a recently introduced multiparticle refinement approach, we obtained a reconstruction of the EIAV CA hexamer at 2.9 Å. Our results demonstrate the potential of the new generation of energy filters and DEDs for STA, and the effects of using different processing pipelines on their STA outcomes.

Enhanced Photocurrent of the Ag Interfaced Topological Insulator Bi2Se3 under UV- and Visible-Light Radiations.

Bi2Se3 is a topological quantum material that is used in photodetectors, owing to its narrow bandgap, conductive surface, and insulating bulk. In this work, Ag@Bi2Se3 nanoplatelets were synthesized on Al2O3(100) substrates in a two-step process of thermal evaporation and magnetron sputtering. X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) revealed that all samples had the typical rhombohedral Bi2Se3. Field-emission scanning electron microscopy (FESEM)-energy dispersive x-ray spectroscopy (EDS), XPS, and HRTEM confirmed the presence of the precipitated Ag. The optical absorptance of Bi2Se3 nanoplatelets in UV-visible range decreased with the Ag contents. Results of photocurrent measurements under zero-bias conditions revealed that the deposited Ag affected photosensitivity. A total of 7.1 at.% Ag was associated with approximately 4.25 and 4.57 times higher photocurrents under UV and visible light, respectively, than 0 at.% Ag. The photocurrent in Bi2Se3 at 7.1 at.% Ag under visible light was 1.72-folds of that under UV light. This enhanced photocurrent is attributable to the narrow bandgap (~0.35 eV) of Bi2Se3 nanoplatelets, the Schottky field at the interface between Ag and Bi2Se3, the surface plasmon resonance that is caused by Ag, and the highly conductive surface that is formed from Ag and Bi2Se3. This work suggests that the appropriate Ag deposition enhances the photocurrent in, and increases the photosensitivity of, Bi2Se3 nanoplatelets under UV and visible light.

Influence of Zinc Doping on the Structural, Morphological, Optical and Electrical Properties of Copper Oxide Thin Films Prepared by Jet-Nebulizer Spray Pyrolysis Technique

This research details the deposition and characterization of adding zinc (Zn) impurities with different doping concentrations (1%, 3%, and 5%) into copper oxide (CuO:Zn) by using a jet nebulizer spray pyrolysis system. The impact of zinc doping on the different copper oxide properties was investigated. The structural studies confirm that pure copper oxide and zinc doped copper oxide thin films are matched with monoclinic structure. High resolution schottky field emission scanning electron microscopy and Energy dispersive spectrum analysis identifies the surface structure and chemical composition of pure CuO and CuO: Zn thin films. EDS spectra reveal the occupancy of Cu, O, and Zn elements in the pure CuO and CuO:Zn thin films. The highest transmittance was observed as 66.91% for 5% Zn concentration. The absorption studies clearly indicated that the absorbance of the films was decreased when Zn doping concentration increase. The energy band gap value (Eg) is calculated as 2.01eV for pure CuO and the value of Eg for CuO:Zn thin films are varied from 2.07 to 2.26 eV. Keithley high resistance and low current electrometer was used to measure direct current conductivity of both pure CuO and CuO: Zn thin films and maximum conductivity value was observed for CuO: Zn (5%) thin film.

Oxygenation of Diamond Surfaces via Hummer’s Method

Oxygen bonded with diamond surfaces impacts important properties such as electrical conductivity, Schottky barrier height, field emission, and chemical reactivity. Though processes such as thermal, hydrogen plasma, etc., are efficient in oxidizing the hydrogen-terminated diamond surfaces, the oxidation of pristine diamond surfaces through wet chemical treatments is still in its infancy. Herein, we investigated the efficacy of Hummer’s method, one of the most celebrated chemical oxidation procedures to convert graphite to graphene oxide, to oxidize the pristine diamond surfaces. We attempted to oxidize both microcrystalline diamond powders and polycrystalline diamond wafers. Due to the presence of an acidic oxidative environment and the formation of strong oxidizing agents such as Mn2O7 and MnO3+ during the course of the reaction, Hummer’s method is found to be very effective in oxidizing the pristine diamond surfaces. The degree of oxygen termination is validated through various spectroscopic and surface probe measurements. Microcrystalline diamond powder is more prone to oxidation to polycrystalline diamond wafers due to excess surface area, and many facets with different dangling bond densities are exposed to the oxidizing medium. The experimental observations are endorsed through molecular dynamics simulations.

650-V 4H-SiC Planar Inversion-Channel Power JBSFETs With 55-nm Gate Oxide: Relative Performance of Three Cell Types

Planar 650-V 4H-silicon carbide (SiC), inversion-channel, 55-nm gate oxide junction barrier Schottky field effect transistors (JBSFETs) with three types of cells are compared in this article for the first time. Devices with linear, hexagonal, and octagonal layouts were fabricated in a commercial foundry. The JBS diode was integrated within each cell type. The Schottky contact width for the JBS diode was adjusted to optimize third-quadrant ON-state voltage drop to below 2.5 V for each cell type to ensure by-passing the body diode while maintaining good blocking characteristics in the first quadrant. The hexagonal cell case was the only one whose breakdown voltage (560 V) fell below the 650-V rating. The highest breakdown voltage (710 V) was observed with the octagonal cell layout with a low leakage current of 10 nA at 600 V. The lowest specific ON-resistance was observed for the hexagonal cell design. However, its gate-drain charge was twice that of the conventional linear cell design and four times that of the octagonal cell design. The data from this work demonstrate that the best overall performance for the 650-V SiC, inversion-channel, 55-nm gate oxide junction barrier Schottky field effect transistors is achieved by using the octagonal cell design.

A Schottky diode and FET‐paralleled analogue predistorter for 5G small‐cell base stations

This letter presents an analogue predistorter (APD) named Schottky diode (SD) and field effect transistor (FET)-paralleled APD (SDFP-APD) for the fifth-generation (5G) mobile system, which is composed of an FET paralleled with two SDs. The simulation results show that the SDFP-APD has the best compression compensation for the radio frequency power amplifier (RFPA) among the SD-APD, the FET-APD and the SDFP-APD. Furthermore, the measurement results illustrate that the SDFP-APD can improve the adjacent channel leakage ratio of the RFPA with the best linearisation performance among the three APDs and reduce the error vector magnitude while applying a 100-MHz bandwidth 5G new radio signal. The proposed SDPF-APD can be a promising linearisation technique for 5G small-cell base stations.

Analysis of reverse leakage mechanism in recess-free thin-barrier AlGaN/GaN Schottky barrier diode

In this letter, the reverse leakage mechanism of thin-barrier AlGaN/GaN Schottky barrier diode (SBD) with recess-free technology is reported for the first time. Two types of SBD were fabricated with different AlGaN barrier thickness (5 and 7 nm). It is found that trap-assisted tunneling is the dominant mechanism for area-related leakage current in the Schottky region at low reverse bias, which attributed to the traps introduced by fluorine-based dry etch during opening the LPCVD SiN x cap. When it is highly reverse biased, Schottky edge leakage current becomes dominant for 7 nm SBD, but not for the 5 nm SBD. The suppression of edge leakage in the 5 nm SBD is due to the reduction of the Schottky edge electric field caused by the thinning of the barrier, which was verified by simulation. These findings will help to further optimize the performance of AlGaN/GaN SBD.

THz power optimization and analysis of plasmonic unbiased photoconductive THz emitters coupled to a spiral-like dipole antenna

We propose a new spiral-like dipole antenna-coupled and unbiased terahertz (THz) photomixer with plasmonic unsymmetrical interdigitated electrodes (UIEs). Each electrode pair is made of subwavelength metal–semiconductor–metal (MSM) structures constituting heterogeneous Schottky contacts. From the optical view and analysis of the electrical transport in the semiconductor, by applying a systematic procedure to achieve optimum design, it is possible to benefit from advantages of having high THz photocurrent derived from the plasmonic enhanced optical absorption and, hence, photogeneration as well as severe built-in Schottky field in the photoconductor. Furthermore, from the electromagnetic view, by introducing an output resonant THz antenna having great impedance matching with the photomixer device, the efficiency of free-space coupling has significantly been enhanced. By exploiting all aspects of design, it has been provided to achieve the THz power of 409 µW from the spiral-like dipole antenna coupled to the proposed plasmonic UIEs with 10 × 10 µ m 2 active area and pitch of Λ = 395 n m . This is more than 1 order of magnitude larger THz power than the highest THz power radiated from the same area of a conventional dipole antenna-coupled unbiased array of the near-field emitters. Also, this improvement is more than 3 orders of magnitude higher THz power as compared with the power radiated from a non-plasmonic far-field operating antenna-less THz chip of the same size.

Characterization of a time-resolved electron microscope with a Schottky field emission gun.

The rapid growth of the field of time-resolved and ultrafast electron microscopy has been accompanied by the active development of new instrumentation. Recently, time-resolved microscopes equipped with a field emission gun have been introduced, demonstrating great potential for experiments that benefit from the high brightness and coherence of the electron source. Here, we describe a straightforward design of a time-resolved transmission electron microscope with a Schottky field emission gun and characterize its performance. At the same time, our design gives us the flexibility to alternatively operate the instrument as if it was equipped with a flat metal photocathode. We can, thus, effectively choose to sacrifice brightness in order to obtain pulses with vastly larger numbers of electrons than from the emitter if for a given application the number of electrons is a crucial figure of merit. We believe that our straightforward and flexible design will be of great practical relevance to researchers wishing to enter the field.

Development and Application of Ultrafast Transmission Electron Microscope Based on Schottky Field Emission

Development and Application of Ultrafast Transmission Electron Microscope Based on Schottky Field Emission