scholarly journals Carbon Nanotube Electron Sources: From Electron Beams to Energy Conversion and Optophononics

2014 ◽  
Vol 2014 ◽  
pp. 1-23 ◽  
Author(s):  
Alireza Nojeh
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Electron Emission ◽  
Electron Beams ◽  
Thermionic Emission ◽  
Secondary Emission ◽  
Electron Sources ◽  
Field Emitters ◽  
Electron Microscopes ◽  
Electron Emitters

Carbon nanotubes have a host of properties that make them excellent candidates for electron emitters. A significant amount of research has been conducted on nanotube-based field-emitters over the past two decades, and they have been investigated for devices ranging from flat-panel displays to vacuum tubes and electron microscopes. Other electron emission mechanisms from carbon nanotubes, such as photoemission, secondary emission, and thermionic emission, have also been studied, although to a lesser degree than field-emission. This paper presents an overview of the topic, with emphasis on these less-explored mechanisms, although field-emission is also discussed. We will see that not only is electron emission from nanotubes promising for electron-source applications, but also its study could reveal unusual phenomena and open the door to new devices that are not directly related to electron beams.

Emission and Processing Requirements for Carbide Films on Mo Field Emitters

1998 ◽  
Vol 509 ◽  
Author(s):  
W. A. Mackie ◽  
Tianbao Xie ◽  
M.R. Matthews ◽  
P. R. Davis
Keyword(s):  
Electron Emission ◽  
Thermionic Emission ◽  
Hydrogen Atmosphere ◽  
Field Emitter ◽  
Electron Sources ◽  
Field Emitter Arrays ◽  
Ion Thrusters ◽  
Field Emitters ◽  
Carbide Coatings ◽  
Small Spot

AbstractWe have been working for many years on electron emission and surface properties of transition metal carbides. These studies have covered field, photo, and thermionic emission from bulk carbides as well as field and photo emission from carbide coatings and films on various substrates. Thin film carbide overcoatings have also been used on field emitter arrays of both Mo and Si. These unique carbide materials have electron emission properties making them attractive candidates for several applications. Uses for these carbides include FEA video displays, microwave applications, high current and small spot electron sources (e.g. accelerators and FELs), and cold cathodes for operation at tube pressures and in poor vacuums (e.g. FEAs, vacuum detectors, and neutralizing beams for ion thrusters).We report here on one aspect of our current research which deals with electron emission of ZrC films coating single Mo field emitters. The relevant application is Spindt-type field emitter arrays. Processing steps are evaluated showing the need for a clean substrate. After deposition treatments are also investigated. Emission degradation has been noted after exposure to air and we report on successful use of a hydrogen atmosphere to reverse those adverse effects.

scholarly journals Effect of heating and resistance on emission properties of carbon nanotubes

2018 ◽  
Vol 2 (2) ◽  
Author(s):  
Sergey V. Bulyarskiy 1 ◽  
Alexander A. Dudin 1 ◽  
Alexander V. Lakalin 1 ◽  
Andrey P. Orlov 1 ◽  
Alexander A. Pavlov 1 ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Thermionic Emission ◽  
Negative Resistance ◽  
Cvd Method ◽  
Field Emission Current ◽  
Multi Walled Carbon Nanotube ◽  
Voltage Current Characteristic ◽  
Field Emission Of Electrons ◽  
A Current

We have studied the effect of the series resistance on the heating of the cathode, which is based on carbon nanotubes and serves to realize the field emission of electrons into the vacuum. The experiment was performed with the single multi-walled carbon nanotube (MCNT) that was separated from the array grown by CVD method with thin-film Ni-Ti catalyst (nickel 4 nm / Ti 10 nm). The heating of the cathode leads to the appearance of a current of the thermionic emission. The experimental voltage current characteristic exhibited the negative resistance region caused by thermal field emission. This current increases strongly with increasing voltage and contributes to the degradation of the cold emitter. The calculation of the temperature of the end of the cathode is made taking into account the effect of the phenomenon that warms up and cools the cathode. We have developed a method for processing of the emission volt-ampere characteristics of a cathode, which relies on a numerical calculation of the field emission current and the comparison of these calculations with experiments. The model of the volt-ampere characteristic takes into account the CNT’s geometry, properties, its contact with the catalyst; heating and simultaneous implementation of the thermionic and field emission. The calculation made it possible to determine a number of important parameters, among which the voltage and current of the beginning of thermionic emission, the temperature distribution along the cathode, the resistance of the nanotube. The phenomenon of thermionic emission from CNT’s was investigated experimentally and theoretically. The conditions of this type emission occurrence were defined. The results of the study could form the basis of theory of CNT emitter’s degradation.

LaB6 nanowires and their field emission properties

2005 ◽  
Vol 901 ◽  
Author(s):  
Han Zhang ◽  
Jie Tang ◽  
Qi Zhang ◽  
Gongpu Zhao ◽  
Guang Yang ◽  
...  
Keyword(s):  
Field Emission ◽  
High Performance ◽  
Rectangular Cross Section ◽  
Chemical Vapor ◽  
Emission Current Density ◽  
Chemical Vapor Deposition Method ◽  
Emission Properties ◽  
Field Emission Properties ◽  
Electron Microscopes ◽  
Electron Emitters

AbstractFor field-induced electron emission, the two factors that enable a high emission current density at low applied voltages are (a) low work function of the emitter and (b) sharpness of the emitter tip. We have developed and applied a chemical vapor deposition method to synthesize single-crystalline LaB6 nanowires for applications as point electron emitters. The crystallographic orientation of the grown nanowires can be controlled by the catalysts used in synthesis and their typical diameter is ranged from below 20 nm to over 100 nm. The nanowires’ tip is either hemispherical or flat top with rectangular cross-section depending on the catalyst being utilized. The field emission properties have also been measured from the single nanowire emitters and the results are discussed for applications as point electron sources used in high performance electron optical instruments such as the transmission and scanning electron microscopes.

scholarly journals Conjugated polyelectrolyte nano field emission adlayers

2016 ◽  
Vol 1 (4) ◽  
pp. 304-312 ◽  
Author(s):  
M. T. Cole ◽  
R. J. Parmee ◽  
A. Kumar ◽  
C. M. Collins ◽  
M. H. Kang ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Electron Emission ◽  
Field Electron Emission ◽  
Conjugated Polyelectrolyte ◽  
Emission Performance ◽  
Field Electron ◽  
Multi Walled Carbon Nanotubes ◽  
Vertically Aligned ◽  
Walled Carbon Nanotubes

Here we report on a straightforward and rapid means of enhancing the field electron emission performance of nascent vertically aligned multi-walled carbon nanotubes by introducing a polar zwitterionic conjugated polyelectrolyte adlayer at the vacuum–emitter interface.

Degradation of Vertically Aligned Carbon Nanotubes at Growth Interface Joints at High Temperatures and Its Impact on Electron Emission Properties

2008 ◽  
Vol 1137 ◽  
Author(s):  
Feng Jin ◽  
Yan Liu ◽  
Chris Day ◽  
Scott Little
Keyword(s):  
Carbon Nanotubes ◽  
High Temperatures ◽  
Electron Emission ◽  
Morphological Changes ◽  
Chemical Vapor ◽  
Growth Interface ◽  
Emission Properties ◽  
Field Emission Properties ◽  
Electron Emitters ◽  
Morphology Changes

AbstractDegradation of carbon nanotubes (CNTs) significantly affects CNT's electron emission capability and limits their applications as electron emitters. In this study, CNTs were placed in controlled environment and their degradations were studied. Two types of CNT degradations, thermal and chemical degradations were identified and their effects on electron emission were studied. It was found that CNTs placed in low vacuum environment at high temperature were subject to oxidation that led to severe degradation of CNTs and their electron emission ability, whereas, CNTs treated at the same high temperatures in an ultrahigh vacuum environment only suffered from morphological changes that had minor impact on electron emission. The CNT samples used in this study were grown on tungsten substrates via plasma enhanced chemical vapor deposition (PE-CVD). The surface morphology changes of the CNT emitters were examined using scanning electron microscopy (SEM). The field emission properties of the CNTs were measured and correlated to the morphology changes.

Thermionic and Photon-Enhanced Emission from CVD Diamond: Influence of Nanostructure, Doping, and Substrate

2014 ◽  
Vol 95 ◽  
pp. 1-10 ◽  
Author(s):  
Tian Yin Sun ◽  
Franz A.M. Koeck ◽  
Robert J. Nemanich
Keyword(s):  
Electron Emission ◽  
Diamond Films ◽  
Thermionic Emission ◽  
Emission Spectra ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Multilayered Structures ◽  
Band Bending ◽  
Controlled Morphology ◽  
Electron Emitters

Thermionic electron emitters based on doped diamond films have shown significant emission at less than 500°C. Results have established that it is necessary to control the electron affinity, doping levels and concentration, and band bending, and these properties have been achieved with engineered multilayered structures with controlled morphology, doping and substrate. Recently, visible light photo-electron emission has been demonstrated using the same diamond film emitters. This report presents a spectroscopic and surface electron microscopy study of photo-and thermionic emission from nitrogen doped diamond films with controlled morphology on metal substrates. Electron emission spectra were recorded to 500°C, while illuminated with sub diamond band gap light. Significant photo-induced emission was observed with an efficiency greater than metal photo cathodes.

Field Electron Emission from Carbon Nanotube Films on Diamond Films

2005 ◽  
Vol 475-479 ◽  
pp. 3587-3590
Author(s):  
K.J. Liao ◽  
W.L. Wang ◽  
Y.T. Wang ◽  
J.W. Lu ◽  
X.L. Sun
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Field Emission ◽  
Electron Emission ◽  
Diamond Films ◽  
Chemical Vapour ◽  
Polycrystalline Diamond ◽  
Field Electron Emission ◽  
Field Electron ◽  
Nanotube Films

The field electron emission from carbon nanotube films on polycrystalline diamond films was investigated. The carbon nanotubes and diamond films on Si substrates were prepared by a conventional hot filament chemical vapour deposition. The films obtained were characterized by scanning electron microscopy and Raman spectroscopy. The field emission properties of the samples were measured in an ion-pumped vacuum chamber at a pressure of 10-6 Pa.. The experimental results showed that the field emission behaviours of carbon nanotubes/diomond films structure have greatly been improved as compared with carbon nanotubes and diamond films, respectively. A turn-on field of 1.0 V/µm and a maximum current of 500 µA at 1.5 V/µm were observed, which were lower than those of carbon nanotubes and polycrystalline diamond films, respectively. This improvement was attributed to the tip shape of sample surface, which provided an additional local increase in electric field at the tube ends.

DETECTION OF INERT GASES BY COLD ELECTRON EMISSION FROM CARBON NANOTUBE EMITTERS

2005 ◽  
Vol 19 (24) ◽  
pp. 1207-1211 ◽  
Author(s):  
SEONGJEEN KIM
Keyword(s):  
Carbon Nanotubes ◽  
Gas Sensors ◽  
Electron Emission ◽  
Dark Current ◽  
Gas Adsorption ◽  
Inert Gases ◽  
Inert Gas ◽  
Gas Composition ◽  
Cold Electron ◽  
Electron Emitters

In this work, different from the typical gas sensors responding by gas adsorption on their surface, a new gas sensor using carbon nanotubes (CNTs) as electron emitters is introduced for detecting inert gases which hardly possess chemical or electrical adsorption in normal conditions. The proposed sensor works by figuring out the variation of the dark current and the initial breakdown voltage on Paschen's law under applied high voltage. As they depend on the gas composition and the pressure in a sealed chamber, it is possible to detect the identity and the concentration of unknown inert gas species.

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