Composite Metallic Nano Emitters Coated with a Layer of Insulator Covered by Au Layer

2020 ◽  
Vol 13 (3) ◽  
pp. 253-262
Keyword(s):  
Thin Layer ◽  
Dielectric Material ◽  
Electrochemical Etching ◽  
Emission Current Density ◽  
Composite Cathode ◽  
Emission Current ◽  
Dielectric Thin Films ◽  
Current Voltage ◽  
Before And After ◽  
New Type

Abstract: In this work, the differences in the behavior and properties of the emitted electron beam from tungsten (W) tips were studied before and after coating these tips with a thin layer of dielectric material followed by a thin layer of gold, to improve the emission current density, stability and emission current pattern concentration. The core of the composite cathode is made of high-purity tungsten (W). Measurements have been made with clean W emitters before and after coating these tips with two types of epoxy resins (epoxy 478 resins or epoxy UPR- 4 resins) followed by a thin layer of gold. For critical comparison, several tungsten tips with various apex-radii have been prepared using electrochemical etching techniques. The emitters have been coated by dielectric thin films of various thicknesses and the layer of Au used for coating the Epoxy layer has the same thicknesses. Their behavior has been recorded before and after the process of coating. These measurements include the current-voltage (I-V) characteristics and Fowler-Nordheim (F-N) plots. Imaging has also been done using a visible light microscope (VLM), along with a scanning electron microscope (SEM) to help in characterizing the epoxy layer thickness on the tip surface after coating. Besides, the emission patterns have been recorded from the phosphorescent screen of a field electron emission microscope (FEM). Having two types of composite systems tested under similar conditions provided several advantages. These measurements helped in producing a new type of emitters that have more suitable features with each of the two resins. Keywords: Cold field emission, Nano emitter, Dielectric coating, Au layer.

Analysis of the Various Effects of Coating W Tips with Dielectric Epoxylite 478 Resin or UPR-4 Resin Coatings under Similar Operational Conditions

2020 ◽  
Vol 13 (3) ◽  
pp. 191-199
Keyword(s):  
Epoxy Resins ◽  
Dielectric Material ◽  
Electrochemical Etching ◽  
Dielectric Thin Films ◽  
Operational Conditions ◽  
Critical Comparison ◽  
Composite Systems ◽  
Current Voltage ◽  
Before And After ◽  
New Type

Abstract: The objective of this work is to study the differences that occur in behavior and properties of the emitted electron beam from tungsten (W) tips before and after coating these tips with a thin layer of a good proven dielectric material. Core metallic tips have been prepared from a polycrystalline (99.995% purity) tungsten (W) wire. Analysis has been carried out for clean W emitters before and after coating these tips with two differences types of epoxy resins; namely: (Epoxylite 478 and UPR-4). For critical comparison and analysis, several tungsten tips with various apex- radii (very sharp) have been prepared with the use of electrochemical etching techniques. The tips have been coated by dielectric thin films of various thicknesses. Their characteristics have been recorded before and after the process of coating. These measurements have included the current-voltage (I-V) characteristics, Fowler-Nordheim (F-N) plots, visible light microscope (VLM) image and scanning electron microscope (SEM) micrographs to measure the influence of the Epoxylite resin coating’s thickness on the tips after coating. Special distributions have been recorded from the phosphorescent screen of a field electron emission microscope as well. Comparing the two sets of composite systems tested under similar conditions has provided several advantages. Recording highly interesting phenomena has produced a wide opportunity to develop a new type of emitter that includes the most beneficial features of both types. Keywords: Cold field emission, Epoxylite 478, Epoxylite UPR-4.

scholarly journals Effects of Antimony Deposition on Field-Emission Current Density of Ge/Si

2021 ◽  
Vol 9 (2) ◽  
Author(s):  
Veronika Burobina
Keyword(s):  
Field Emission ◽  
Current Density ◽  
Emission Current Density ◽  
Emission Current ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Field Emission Current ◽  
Current Voltage ◽  
Field Emission Current Density ◽  
20 Nm

Abstract To estimate the field-emission current density of a Ge/Si heterosystem, 20-nm germanium/silicon (100) samples were grown by molecular beam epitaxy. The surface of one sample was covered with a layer of antimony, which was removed in vacuum prior to the samples being measured. A second sample of Ge/Si was exposed to room air in the absence of antimony. The current–voltage characteristics of both samples obtained by scanning tunneling microscopy (STM) were discovered to be in agreement with classical Fowler–Nordheim theory. The density of emission current from Ge nanocrystal exceeds the density of emission current from the wetting layer of Ge/Si. The density of emission current of pure Ge nanocrystal is less than the density of emission current of Ge nanocrystal with adsorption layers.

A New Thermionic Cathode Based on Carbon Nanotubes with a Thin Layer of Low Work Function Barium Strontium Oxide Surface Coating

2008 ◽  
Vol 1142 ◽  
Author(s):  
Feng Jin ◽  
Yan Liu ◽  
Scott A Little ◽  
Chris M Day
Keyword(s):  
Work Function ◽  
Current Density ◽  
Enhancement Factor ◽  
Thermionic Emission ◽  
Field Enhancement ◽  
Oxide Coating ◽  
Emission Current Density ◽  
Emission Current ◽  
Strontium Oxide ◽  
Barium Strontium

ABSTRACTWe have created a thermionic cathode structure that consists of a thin tungsten ribbon; carbon nanotubes (CNTs) on the ribbon surface; and a thin layer of low work function barium strontium oxide coating on the CNTs. This oxide coated CNT cathode was designed to combine the benefits from the high field enhancement factor from CNTs and the low work function from the emissive oxide coating. The field emission and thermionic emission properties of the cathode have been characterized. A field enhancement factor of 266 and a work function of 1.9 eV were obtained. At 1221 K, a thermionic emission current density of 1.22A/cm2 in an electric field of 1.1 V/μm was obtained, which is four orders of magnitude greater than the emission current density from the uncoated CNT cathode at the same temperature. The high emission current density at such a modest temperature is among the best ever reported for an oxide cathode.

Anomalous Scatter of Forward Current-Voltage Characteristics of He+-Irradiated Ni/4H-SiC Schottky Diodes

2016 ◽  
Vol 858 ◽  
pp. 749-752 ◽  
Author(s):  
Anatoly M. Strel'chuk ◽  
Viktor V. Zelenin ◽  
Alexei N. Kuznetsov ◽  
Joseph Tringe ◽  
Albert V. Davydov ◽  
...  
Keyword(s):  
Series Resistance ◽  
Degradation Mechanism ◽  
Schottky Diodes ◽  
Defect Structures ◽  
Induced Current ◽  
Forward Current ◽  
Current Voltage ◽  
Before And After ◽  
Current Voltage Characteristics

A study of forward current-voltage characteristics of Ni/4H-SiC Schottky diodes (SDs) before and after irradiation with He+ ions revealed features that characterize defect structures and reveal the degradation mechanism of the diodes. These features are the presence of excess currents of certain type in the unirradiated SDs, their appearance in forward-biased originally ideal SDs, and a >10 orders of magnitude scatter of the series resistance of the SDs upon their irradiation with He+ ions. A model of localized defect-induced current paths (shunts) in the form of unintentionally produced SDs with the substrate is suggested.

scholarly journals Effect of CaO on Phase Composition and Properties of Aluminates for Barium Tungsten Cathode

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1380 ◽  
Author(s):  
Jinglin Li ◽  
Jianjun Wei ◽  
Yongbao Feng ◽  
Xiaoyun Li
Keyword(s):  
Single Phase ◽  
Emission Current Density ◽  
Environmental Stability ◽  
Precipitation Method ◽  
Pulse Emission ◽  
Molar Amount ◽  
Mixture Phase ◽  
Before And After ◽  
Method Effects ◽  
Co Precipitation

6BaO·xCaO·2Al2O3 (x = 0.8, 1.2, 1.6, 2, and 2.2) aluminates were synthesized via a liquid phase co-precipitation method. Effects of the molar amount of CaO on the phase of aluminates before and after melting and their hygroscopic phase, melting properties, environmental stability, evaporation, and emission properties were systematically studied. The results show that with the increase of the molar amount of CaO, the aluminates change from a mixture phase to a single phase of Ba3CaAl2O7, and the diffraction peak shifts to a higher angle. The melted phase of the aluminates changed from a single phase to a mixed phase of Ba5CaAl4O12 and Ba3CaAl2O7. Meanwhile, the comprehensive properties of the aluminates are improved. The weight gain of 6BaO·2CaO·2Al2O3 aluminates is only 10.88% after exposure to air for 48 h; the pulse emission current density of barium tungsten cathodes impregnated with 6BaO·2CaO·2Al2O3 aluminates in the porous tungsten matrix can reach 28.60 A/cm2 at 1050 °C, and the evaporation rate is 2.52 × 10−10 g/(cm2·s).

Isometric Stress Analysis and Current-Voltage Characteristics of Some Nanoclay Dielectric Elastomer Compounds

2007 ◽  
Author(s):  
N. Nurminen ◽  
A. Ellman ◽  
V. Jouppila ◽  
M. Paajanen ◽  
M. Karesoja
Keyword(s):  
Material Model ◽  
Dielectric Elastomer ◽  
Adhesive Tape ◽  
Electromechanical Properties ◽  
Dependent Behavior ◽  
Current Voltage ◽  
New Type ◽  
Current Voltage Characteristics ◽  
Compound Materials ◽  
Different Levels

The electromechanical properties of elastomer material change when different levels of stretching are applied to the elastomer film. The generated stress and expansion of the EAP material depend on the electric field across the material and its relative permeability. Some of the best known commercial dielectric elastomer materials are based on acrylic elastomers, e.g. 3M VHB 4910 or 4905 adhesive tape. In this work, the VHB 4910 tape was used as a reference material for different types of acrylic nanoclay compound materials. These new type of nanoclay elastomer compounds were tested because the addition of clay into the elastomer was assumed to increase its actuating performance. Different voltage and pre-stretching levels were used in the measurements. Current-voltage characteristics and isometric stress measurements were used to study the energy efficiency, frequency dependent behavior, reactivity and isometric stress performance of the EAP materials. Based on the electromechanical characterization and material properties, a general hyperelastic material model was developed. According to the preliminary tests, the nanoclay compound seems to be a bit stiffer than VHB 4910 resulting in a greater isometric stress response.

High emission current density, vertically aligned carbon nanotube mesh, field emitter array

2010 ◽  
Vol 97 (11) ◽  
pp. 113107 ◽  
Author(s):  
Chi Li ◽  
Yan Zhang ◽  
Mark Mann ◽  
David Hasko ◽  
Wei Lei ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Current Density ◽  
Emission Current Density ◽  
Emission Current ◽  
Field Emitter ◽  
High Emission ◽  
Vertically Aligned ◽  
Emitter Array ◽  
Field Emitter Array

scholarly journals Mathematical models for thermionic emission current density of graphene emitter

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Olukunle C. Olawole ◽  
Dilip K. De ◽  
Sunday O. Oyedepo ◽  
Fabian I. Ezema
Keyword(s):  
Mathematical Models ◽  
Current Density ◽  
Coefficient Of Thermal Expansion ◽  
Thermionic Emission ◽  
Emission Current Density ◽  
Least Square ◽  
Emission Current ◽  
Two Dimensional Materials ◽  
Current Emission ◽  
Thermionic Energy

AbstractIn this study, five mathematical models were fitted in the absence of space charge with experimental data to find a more appropriate model and predict the emission current density of the graphene-based thermionic energy converter accurately. Modified Richardson Dushman model (MRDE) shows that TEC's electron emission depends on temperature, Fermi energy, work function, and coefficient of thermal expansion. Lowest Least square value of $$S=\sum {\left({J}_{th}-{J}_{exp}\right)}^{2}=0.0002 \,\text{A}^{2}/\text{m}^{4}$$ S = ∑ J th - J exp 2 = 0.0002 A 2 / m 4 makes MRDE most suitable in modelling the emission current density of the graphene-based TEC over the other four tested models. The developed MRDE can be adopted in predicting the current emission density of two-dimensional materials and also future graphene-based TEC response.

Absolute emission current density of O− from 12CaO⋅7Al2O3 crystal

2002 ◽  
Vol 80 (22) ◽  
pp. 4259-4261 ◽  
Author(s):  
Q. X. Li ◽  
K. Hayashi ◽  
M. Nishioka ◽  
H. Kashiwagi ◽  
M. Hirano ◽  
...  
Keyword(s):  
Current Density ◽  
Emission Current Density ◽  
Emission Current

A new multiscale approach to rapidly determine the local emission current density of nanoscale metallic field emitters

2021 ◽  
Vol 130 (14) ◽  
pp. 144302
Author(s):  
J. Ludwick ◽  
M. Cahay ◽  
N. Hernandez ◽  
H. Hall ◽  
J. O’Mara ◽  
...  
Keyword(s):  
Current Density ◽  
Emission Current Density ◽  
Emission Current ◽  
Multiscale Approach ◽  
Field Emitters ◽  
Local Emission
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