Fabrication of a new cold cathode based on pulsed laser deposition of lanthanum monosulfide thin films
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Field emission properties of lanthanum monosulfide (LaS) thin films deposited by pulsed laser deposition (PLD) have been measured by building an array of new cold cathodes based on MEMS technology. The new cold cathode array has been fabricated by a sequence of steps on two separateKeywords:
Pulsed Laser Deposition
Lanthanum
Deposition
Cold cathode
A theoretical study of properties of the auxiliary cathode of magnetrons with cold secondary-emission cathodes is performed. Different methods of providing a spatial-charge limited emission from the auxiliary cathode are studied in order to eliminate the temperature dependence of the emission current. New designs of the auxiliary cathode are proposed to provide a better emission current stability with respect to temperature variations, as compared to the currently used cathodes in spatialharmonic mm-wavelength magnetrons.
Cold cathode
Hot cathode
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Abstract The introduction of secondary ion-electron emission into an approximate model of non-equilibrium plasma layers on hot (thermionic) cathodes of high-pressure arc discharges allows extending the model to low cathode surface temperatures. Analysis of evaluation results shows that the extended model describes glow-like discharges on cold cathodes and thermionic arc discharges on hot cathodes, as it should. In the course of glow-to-arc transitions on cold cathodes, a transient regime occurs where a hot arc spot has just formed and a significant fraction of the current still flows to the cold surface outside the spot, so that the near-cathode voltage continues to be high. The power input in the near-cathode layer is very high in this regime, and so is the electron temperature in the near-cathode region. The mean free path for collisions between the atoms and the ions in these conditions exceeds the thickness of the layer where the ion current to the cathode is generated. A new method for evaluation of the ion current under such conditions is implemented. The developed model is applicable for cathode surface temperatures below the boiling point of the cathode material and may be used for multidimensional simulations of ignition of high-current arcs on refractory cathodes.
Hot cathode
Thermionic emission
Cold cathode
Cathodic arc deposition
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In cross-field microwave devices the total operating current usually consists of two components: the primary excitation current and the main operating current built up by the secondary electrons. As a source of primary current the cathode based on a cold field emission could be used]. Cold cathodes based on the phenomenon of field emission have a number of advantages over regular thermionic emission cathodes. They emit electrons at room temperature, do not require warm-up time, and are capable of producing very high current densities. However, cold cathodes are very sensitive to the bombardment by ions of residual gases, which sputter the cathode surface material and cause degradation of cathode's characteristics. Generally the cathode consists of the series of film field and secondary emitters placed on the supporting rod. When the cathode is operated within a strong electric field with sufficient magnitude to cause field emission, electrons will begin to leave the emitter's surface. Electrons within the interaction space will be accelerated toward the anode and will follow trajectories consistent with the electric and magnetic fields present within the magnetrons interaction space. Some of these dislodged electrons will return to the cathode with enough energy to dislodge further electrons. These dislodged electrons will enter the interaction space and the process repeats itself until high voltage is removed from the device.
Cold cathode
Thermionic emission
Hot cathode
Secondary emission
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In the present paper the 3-D model is employed to analyze the electron hub generation process in a magnetron diode with a secondary-emission cathode whose operation is stimulated by priming electrons from ancillary side cathode. It is shown that the electron emitted from the cold cathode areas at the diode ends has an effect upon the rate of space charge density, it is needed to trigger the secondary electron multiplication process over the entire operating surface of the main cathode.
Cold cathode
Cavity magnetron
Secondary emission
Hot cathode
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Recently, highly efficient NEA GaP-GaAlP cold-cathodes have been obtained by improving crystal growth conditions. The initial short term degradation modes of continuous operating GaP-GaAlP cold-cathode have been studied, and the following conclusions have been reached: (1) During the thermal cleaning of the p-GaP surface, an irreversible degradation of the cold-cathode occurs due to damage by thermal etching below the optimum temperature for cleaning the surface;(2) a major source of rapid degradation of the cold-cathode is the loss of Cs and/or O2 from the cold-cathode, and therefore the cathode stability can be improved by repeating the activation of surface and by increasing the activation temperature. Continuous operation of GaP cold-cathode over 3000 hours can be achieved.
Degradation
Cold cathode
Thermal Stability
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The Mo-tip field-emitter array (FEA) was applied to the electron gun of the cathode-ray tube (CRT). In order to replace the conventional thermionic cathode with a cold cathode, the Mo-tip FEA was newly designed according to the specification of the CRT electron gun. The electron-emission properties and display performances of the electron gun with a Mo-tip FEA cathode were characterized and discussed. The fabricated electron gun with a Mo-tip FEA cathode showed better performance in terms of emission current and switch-on time. Finally, the potential applicability was guaranteed by means of operating the 19 in. color CRT using the fabricated electron gun with the Mo-tip FEA.
Electron gun
Cold cathode
Thermionic emission
Hot cathode
Vacuum tube
Cathode ray tube
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The operation of hot cathodes in high pressure discharge lamps has been investigated in a manner similar to that described by Ecker5). The formalism of Dyke and Dolan8) has been used to calculated emission of electrons from the cathode as a function of temperature and electric field. The electric field at the cathode surface is calculated from ion current and cathode fall, the largest contribution to that field being developed in the free-fall sheath less than one mean free path in thickness at the cathode surface. Two solutions to the coupled system of equations are found: a low-field, diffuse-mode solution in which electron emission is by the Shottky-amplified thermionic process, cathode fall increases with increasing current density, and the cathode spot tends to expand to fill the entire extent of the cathode tip; and a high field, hot-spot mode in which electrons are emitted as a result of the temperature-field mechanism. The lowest cathode fall in the latter mode occurs when the potential drop across the free fall sheath equals the cathode fall required by the cathode energy balance. The operating mode of the discharge in a given lamp depends on which of the two modes has the lowest cathode fall. Examples of each occur in various lamps and can be accounted for with reasonable values of material constants. It is shown that the hot-spot mode is favored over the diffuse mode by high pressures and low cathode work function. The latter surprising result is accounted for by the fact that field emission, varying as exp (-φ3/2), is even more favored by low work function than thermionic emission.
Cold cathode
Thermionic emission
Hot cathode
Gas-discharge lamp
Voltage drop
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Recently, highly efficient NEA GaP-GaAlP cold-cathodes have been obtained by improving crystal growth conditions. The initial short term degradation modes of continuous operating GaP-GaAlP cold-cathode have been studied, and the following conclusions have been reached: (1) During the thermal cleaning of the p-GaP surface, an irreversible degradation of the cold-cathode occurs due to damage by thermal etching below the optimum temperature for cleaning the surface;(2) a major source of rapid degradation of the cold-cathode is the loss of Cs and/or O2 from the cold-cathode, and therefore the cathode stability can be improved by repeating the activation of surface and by increasing the activation temperature. Continuous operation of GaP cold-cathode over 3000 hours can be achieved.
Cold cathode
Degradation
Thermal Stability
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The field-emission cathode has potential application in the field emission display panels, high frequency amplifiers, X-ray sources, cathodoluminescent light sources. Many research works have been focused on the improvement of field-emission performance of a carbon nanotube cathode. A few methods, such as adhesive taping, soft rubber rolling, mechanical rubbing, plasma etching, and laser irradiating, have been proposed to get large emission current and good emission uniformity. In this paper, a new structure of the cold cathode is proposed. A metal layer is deposited on a cathode substrate as the cathode electrode. The field emitters, such as carbon nanotubes, ZnO nanopods, and etc., are grown on the cathode electrode. Some nano particles with high conductivity are distributed around the cathode electrode by spraying or printing. The result shows the distribution of electric field between a field-emission diode.
Cold cathode
Field emission display
Hot cathode
Rubbing
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A theoretical model of a glow discharge with a cold hollow cathode is introduced which takes into account the contribution to ionization of the gas from fast secondary electrons formed in the cathode layer. The resulting expression for the volt-ampere characteristic agrees satisfactorily with experiment. Including the formation of fast secondary electrons in the layer makes it possible to explain a well-known specific property of the discharge - the direct proportionality, for a constant cathode potential drop, of the width of the cathode layer to the width of the cathode hollow. 15 references.
Cold cathode
Glow discharge
Secondary emission
Penning ionization
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