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This tutorial lecture provides an introduction (suitable for those relatively new to the subject) to methods available for the extraction of emitter characterization data from field electron emission (FE) current-voltage data, to the problems of doing this reliably, and to some recent progress in developing better understanding of the issues involved.
Field emission from “nano diodes” encounter strong deviations from the tunneling barrier presupposed in Fowler Nordheim theory. Modifications to the emission barrier are modeled using a hyperbolic geometry to find trajectories along which Gamow factor is found; a quadratic equivalent potential is determined, and a shape factor method is used to evaluate the total current from a protrusion or wedge...
Energies of emitted electrons from n-type diamond NEA surface and graphene/n-type diamond junction were measured by combined field emission spectroscopy/ultraviolet photoelectrons spectroscopy (FES/UPS) system. For n-type diamond NEA surface, the energies of emitted electrons indicated that the electrons emitted from conduction band of the diamond. For graphene/diamond junction, electron emission...
A new model of low-field electron emission is proposed, presumably applicable for nanostructured materials possessing neither the quality of low work function nor capability of field enhancement at high-aspect-ratio elements. In accordance with the model, hot-electron emission is ultimately driven by thermoelectric phenomena developing near nanosized emission centers. Numerical estimates were performed...
We report on an extended use of the Fowler-Nordheim plot for energetic evaluation of charge transfers in vacuum electronics. First results explained clearly, the transition from field electron emission to plasma discharge is physically conditioned, especially in the case of higher emission currents.
Vacuum arcing (also known as breakdown), is a major limiting factor in various applications such as particle accelerators, fusion reactors etc. Although it is well-established that vacuum arcs appear after intense Field electron Emission (FE), the physical mechanism that leads from FE to the ignition of plasma is not yet understood. A common hypothesis is that intense FE leads to excessive heating...
Experimental field emission data from large area field emitters (LAFEs) have been analyzed using a “two-class model”, in which some emitters have a field enhancement factor significantly greater than the remainder. Using parameters derived experimentally, corresponding Fowler-Nordheim plots were theoretically predicted and agree adequately with the “kinked” plots observed experimentally. In the analysis...
We fabricated field emission electron sources and applied for the glass sealed x-ray tube for medical imaging devices. The x-ray tube consists of an electron beam with a patterned grown CNT emitters with RAP process. Those electron beam shows higher electron emission current and transmittance after glass seal. With the x-ray tube, we success to measure medical image with finger and high resolution...
Electron emission induced by picosecond laser from solid surfaces placed under an intense electric field has been modeled. The results show an important difference between the electrons temperature (5500 K) and the phonons temperature (850 K). In these conditions, the Fermi-Dirac distribution depends of the electron temperature, while the thermo-field emission becomes effective for temperatures well...
We report the featured field electron emitter of Si tip with individually integrated nano-channel. A rational procedure was developed to fabricate the uniform integrated device. The Si nano-channel can limit both current and heat flow. The heat resistance of the nano-channel resulted in the heat accumulation at the tip apex, inducing the thermally assisted field electron emission. The negative feedback...
Ion mobility spectrometers (IMS) are measurement devices for fast and ultra-sensitive trace gas analysis. Most IMS employ radioactive electron sources, such as 3H or 63Ni, to provide free electrons with high kinetic energy at atmospheric pressure for initiating a chemical gas phase ionization of the analytes. The disadvantage of these radioactive materials are legal restrictions and the electron emission...
Electron emission from single hot carbon nanotubes (CNTs) heated by self-Joule heating is in situ studied inside a scanning electron microscope (SEM) and the emitted electrons are detected by the Everhart-Thornley detector. Periodic pulsed electron emission is observed to overlap on a dc background. The period of the pulses is measured to be 292 ms with no dependence on the bias voltage applied to...
Improvement of the electron emission properties of the planar-type electron emission devices based on a graphene-oxide-semiconductor (GOS) structure was achieved by vacuum annealing at 300 oC. Electron emission efficiency of GOS type electron emission devices reached 2.7 % from 0.2 % after vacuum annealing. The work function of graphene electrode was found to decrease 0.26 eV after vacuum annealing...
We fabricated a high performance electron beam for the vacuum electronic devices with carbon nanotube (CNT) cathode. For the vacuum electronic devices application, a structure of cold cathode should be highly adhere on cathode substrate and endure a resistive heating during electron emission. For fabrication of stable electron beam, we optimized the CNT emitters and the triode structure. The structural...
We fabricated high resolution electron beam with carbon nanotube cold cathode for microscopy application. The electron beam shows a resolution of 165 μm with phosphor light area measurement and higher emission current more than 60 μA. The electron beam has 9 individual electron sources with CNTs. The electron emission current depend on the length and pitches between CNT emitters. The isolated individual...
As part of a longer-term project to compare different methods of extracting emission-area data from ideal Fowler-Nordheim plots, this Poster investigates refinements to the extraction-parameter approach. It is shown that varying the choice of the scaled fitting parameter ft, depending on the range of values used for the independent variable, does make a noticeable difference. However, the (usually...
This Poster outlines simple general derivations of the correction factors λT=πp/sin(πp) and λF=πq/sin(πq) that first appeared in this form in the 1973 re-formulation by Swanson and Bell of equations originally derived by Murphy and Good in 1956. The original proofs and results apply only to the Schottky-Nordheim barrier. For planar smooth-surface conceptual models, analyzed via the Kemble approach,...
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...
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...
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...
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