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Herein we report, pressure dependent field emission (FE) behaviour of a few-layer graphene emitter. Gas dependent FE properties have been investigated in ultra high vacuum (UHV), as well as in N2 and O2 ambience at base pressure ∼ 1×10−6 torr. Interestingly, the graphene emitter when operated in N2/O2 ambience exhibits lower turn-on field and higher emission current density, as compared to the UHV...
This contribution is an unplanned by-product of high emission current investigations with CNT field-emitter cathodes. A simple self-screening model for individual CNTs is presented. Simulation results are field emission limitations at extremely high and low electron emission currents, and a new evaluation of field enhancement factor.
Laser-driven metal needle emitters offer great potential for low emittance pulsed electron sources as required in ultrafast transmission electron microscopy. Here, we experimentally and theoretically study site-selective photoelectron emission in a field emitter geometry.
Scanning tunnelling microscopy overshadowed other microscopy techniques owing to its unprecedented spatial resolution. However, the lack of secondary electrons in the experiment always motivated the quest for a complementary technique. The topografiner technology - a precursor of the STM - could not meet this task so far. Nevertheless, it still plays an important role in the arsenal of probing techniques...
Ultrafast, optically-triggered field emitter arrays are an exciting new area of research with potential application in ultrafast imaging and in coherent x-ray sources based on inverse Compton scattering. The fabrication and preliminary experimental results of pitch scaling on emitter arrays using n-type silicon wafers and scalable CMOS processing is studied to better understand the effect of tip to...
In this work, we studied light induced thermionic emission from potassium intercalated carbon nanotube forests. Several recipes were developed for the intercalation process. The intercalated CNT forest was employed as the emitter of a light activated thermionic emission device. The resulting thermionic device was characterized by studying its current-voltage characteristics when illuminated by a focused...
In order to evaluate the performance of ZnO nanowire field emission display under different temperature, the temperature dependence of field emission current of a fully-sealed diode-structured field emission device using ZnO nanowire cold cathode was studied when the temperature changed from −60°C to 80°C. The pressure inside the device was also measured. It is found that the emission current decreases...
In order to develop the microwave and millimeter-wave vacuum electronic radiation source devices with field emission cold cathodes, an electron-optical system based on carbon nanotube cold cathode is investigated in this paper. A magnetron injection electron gun is designed for a 220GHz TE03 mode gyrotron. And the preliminary experiment results of the carbon nanotube cathode show the maximum beam...
The field emission heat engine (FEHE) is a novel thermionic converter with strong electric fields applied on the anode and/or cathode, to set up quantum tunneling barriers, so that electrons with energies lower than the surface vacuum level can still escape the cathode, transit the vacuum gap, and ‘inverse tunnel’ into the anode [1]. Notably, by lowering the effective work function of just the anode...
We report the field-induced surface deformation of Si nano-apex and the achieving of highly reliable gated Si nanoemitters. It was found that the crystalline Si nano-apex deformed to amorphous structure at a low macroscopic field (∼0.6 V/nm) with an extremely low emission current (∼1 pA). First-principle calculations showed that the arsenic donor would increase the electric polarization on the Si...
This paper describes observed changes in the emission from a 100-tip Spindt cathode array operated at peak emission levels that produced Joule heating and temperatures sufficient to cause surface self-diffusion at the tips. This well-known thermal field forming effect can produce blunting or sharpening of the emitter tips, depending on whether the thermal self-diffusion, or the field-assisted thermal...
We have designed and fabricated a novel electrostatic lens module composed of a micro- and macro-focusing lens in carbon nanotube field-emission electron guns for energy-variable X-ray sources maintaining their focal spot size. The effective focal spot was observed to be small and isotropic by the micro-focusing lens to suppress the divergence of an individual electron beam and the elliptical macro-focusing...
Micro Hollow Cathode Discharge (MHCD), a technology well known as an ion source, is adapted using Argon to be a cold-cathode electron beam source for applications such as microwave tubes amplifier, which require high total current and high current density. To enable using the MHCD as the electron resource for a microwave tube devices, a focus system has been designed, incorporating an electrostatic...
Operational characteristics of vacuum triodes with a field emitter array with a hafnium nitride emitter, have been investigated in harsh environments. Cnrrent-voltage characteristics up to 300°C or down to −130°C were investigated. Current-voltage characteristics before and after the ion irradiation were also investigated. A long term operation was conducted to ensure the tolerance, and it was found...
This conference poster present an alternative derivation of a well known formula that relates both to the concept of reduced brightness in a charge-particle (CP) beam and to the blurring of field-ion image spots. It is then argued that field ion images provide a practical illustration of some aspects of CP optics, including the issue of whether reduced brightness is always a conserved quantity.
We have studied the photoassisted electron emission from a p-type silicon field emitter array under illumination of laser lights with 633 nm and 405 nm wavelengths. The increase of the emission current under light illumination is proportional to the emission current in the dark. The significant influence of the polarization in photoassisted emission for each wavelength was not observed.
Electron impact ionization and ion implantation processes were performed in a miniature test chamber (0.7 cm3) to investigate the possibility of high vacuum pumping. The test chamber can be connected to or isolated from a pressure-controlled vacuum chamber for precise control of the initial experimental conditions. Despite, ion implantation into the getter (confirmed by SIMS measurements) at quantities...
The characteristics of the x-ray source with the LiTaO3 crystal excited using 0.89-W Nd:YLF and 5.0-W fiber laser lights were measured and compared to each other for the development of the high energy and high dose x-ray source. The maximum x-ray energy from the LiTaO3 x-ray source excited using a 5.0-W fiber laser light was higher than that using a 0.89-W Nd:YLF laser light. The average radioactivity...
The traditional Fowler-Nordheim (FN) equation has been repeatedly shown to fail for highly curved surfaces. In the past there have been modifications to it mostly for spherical surfaces. In this paper we derive a generalized FN-type equation which is valid for all potentials and surfaces. Both the current density at the emitter apex J(θ=0) and the effective emission area are derived rigorously. From...
The non-linear response of matter to ultrashort laser pulses on the (sub)femtosecond scale allows controlling and steering electronic motion. Strong field interaction with condensed matter promises to eventually realize the dream of light-field electronics with devices operating on the femto-second time scale and nanometer length scale. Theoretical exploration of such processes faces the challenge...
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