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The classical equations for describing the electron current density due to field and thermal emission from planar surfaces are unsuitable for modern nanometer-scale emitters. The planar equations are often presented in the form of Murphy and Good who, in their seminal paper [1], provided a method for deriving both the Fowler-Nordheim (FN) and Richardson-Schottky (RS) equations for field and thermal...
The most commonly used theoretical tools for the calculation of electron emission are still nowadays the Fowler-Nordheim and the Richardson-Laue-Dushman equations, although it has been shown since the 1990's that they are inadequate for nanometrically sharp emitters or in the intermediate thermal-field regime. Here we present a recently developed computational method for the calculation of emission...
Magnification of an electrostatic divergent lens with extremely short gap spacing was investigated with computer simulation. The present study focused on the dependence of the magnification on the electrode spacing. The numerical solution showed a relatively good agreement with the analytical value when the ratio of the aperture diameter to the electrode spacing was less than unity. The magnification...
A traveling wave tube (TWT) based on carbon nanotube (CNT) cold cathode is theoretically researched in this paper. A magnetic injection electron gun and helix slow-wave structure is adopted in the TWT. Simulation results show that the maximum output power of the CNT TWT can reach 54 W at 9.4 GHz with an input power of 50 mW, corresponding to the maximum gain of 30 dB, when the gyrating electron beam...
We propose a mathematical model for calculation of performance of field-emission cells. Demonstrated model allow calculating electrical potential distribution, trajectories of the emitted electrons and cell currents. Three different constructions of cell were examined. The main important features for cell performance were defined through the model. We assume that using this model will allow to simplify...
Pulse field emission characteristics of a single carbon nanotube (CNT) were investigated using an in-situ scanning electron microscope combined field emission measurement system. The critical field emission current density was related to the length of CNT. Given a certain pulse period, CNT which is shorter in length, could bear higher electric field strength and achieve higher current density.
Field electron emission patterns emitted from few-layer graphene with different edge morphology were investigated using field emission microscopy (FEM). The FEM image of few-layer graphene was observed as a “lantern”, which is composed of light and dark fringes. The relationship between graphene edge morphology and field emission pattern was investigated using a emission electron spatial interference...
Field Emission Pattern Image of Carbon Nanotubes has been captured by using electron beam scanning analyzer. The measurement showed that the Faraday cup scanning method can provide a high resolution field emission sites distribution measurement (the best resolution is up to 0.01mm), which is higher than that using the transparent anode method.
High power, high frequency vacuum electronic devices require high brightness, low emittance electron beams to operate [1]. To meet these demands, thermionic cathodes encounter challenges with rapid turn-on, lifetime, rapid emission gating, and the system inefficiency of the heater power requirement. Field-emission cathodes can provide sufficient current for hundreds of hours but typically produce...
A cathode material of a low work function is needed to achieve a high performance electron source. We measured the work function of W(100) surface modified with Y2O3 by using of photoemission electron microscope. The work function of Y-oxide/W(100) surface is measured to be 2.5eV. Field emission characteristics is measured with Y-oxide/W emitter and work function is estimated by N-F plots.
Adsorption of barium metal on tungsten (100) and (110) surfaces at 300 K results in a condensed uniform film. Heating the barium metal layer to temperatures of 800–900 K causes the film to convert into spherical metal droplets. The droplets do not wet the W(100) or W(110) surfaces. The measured contact angle between the Ba droplets and the surface is greater than 150 degrees.
In this paper, we report our first experimental findings that evidence the vacuum level in the test chamber can be responsible for variation in the field emission (Fowler-Nordheim) response of an electron source. This situation is exampled using a carbon nanotube sample measured in a parallel plate configuration.
The paper describes electrical noise of experimental field emission cathodes based on “polymer” pencil leads which have a high content of hybridized carbon with a low degree of surface oxidation and silicon monoxide (SiO). Charge transport within experimental samples is evaluated based on results provided by the noise spectroscopy method. The paper also briefly describes the experimental preparation...
Previous experiments have showed that carbon island films (quantum dots) at silicon can be capable of low-field electron emission. This paper presents new results of experiments on comparative characterization of emitting and non-emitting thin carbon films. Auger spectroscopy, Electron Energy Loss Spectroscopy, Anderson's technique for work function measurement and secondary-emission techniques confirmed...
Local emission characteristics of the microscopic emission sites on a surface of large area field emitters is one of the most important factors which establish the macroscopic emission properties. This work is aimed to evaluate the local field emission characteristics using computerized field emission projector and technique of multi-channel recording of IVCs. The model sample is nanocomposite nanotubes...
In this work we present the results of numerical processing of extensive datasets of electron field emission (FE) micrographs obtained from planar nitrogen-incorporated ultra-nanocrystalline diamond ((N)UNCD) films deposited on different substrates. The micrographs were acquired concurrently with the FE measurements performed in a parallel-plate configuration. The extracted electrons were collected...
We report field emission properties of gated p-type silicon field emitter arrays with submicron gate aperture induced by laser pulses. Polarization dependent photoemission is observed and the current shows linear dependence on laser power. The results indicate that the current pulses from our devices are created by photo-field emission process dominantly.
We describe the development of a micrometer-scale photoelectron gun for the implementation of ultrafast low-energy electron diffraction from surfaces. A photolithography process and focused-ion-beam nanostructuring is used to assemble and electrically contact the electron gun, which consists of a nanotip photocathode and an Einzel lens for beam collimation. First time-resolved measurements in a backscattering...
The purpose of the present work is to study anticorrelation between quantum efficiency and spin-polarization, which is a characteristic feature of GaAs photocathodes. We employ the Monte Carlo techniques to simulate in detail the photo-absorption, electron transport, and tunnelling of electrons through the potential barrier at the surface of p-doped GaAs activated to negative electron affinity (NEA)...
We report systematic investigations of the photo- and field induced electron emission from highly doped and highly ordered, flat polycrystalline diamond material by means of photo-field emission spectroscopy. The cathode was operated under pulsed tunable laser illumination (pulse duration tlaser=3.5 ns, photon energy hv=0.5−5.9 eV) in a wide power range of up to 0.7 GW/cm2 und under electrical fields...
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