Stabilization of carbon-fiber cold field-emission cathodes with a dielectric coating

Mousa, Marwan S.; Kelly, Tom

doi:10.1016/s0304-3991(02)00307-8

Cited by 19 publications

(16 citation statements)

References 13 publications

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“…It is found that the field emission characteristics of these micro-emitters are intrinsically changed by coating the emitters with a thin layer of dielectric material, this is in line with the results from previous investigations (AlQudah et al, 2015;Bajic et al, 1989;Latham & Mousa, 1986;Moran Meza et al, 2015;Mousa, 1987Mousa, , 1988Mousa, , 1992Mousa, , 1994Mousa, , 2007Mousa & Kelly, 2003;Mussa et al, 2012). By comparing the effects of different coating materials, we find the following effects.…”

Section: Discussionsupporting

confidence: 90%

Epoxylite Influece on Field Electron Emission Properties of Tungsten and Carbon Fiber Tips

Alnawasreh

Al-Qudah

Madanat

et al. 2016

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This investigation deals with the process of field electron emission from composite microemitters. Tested emitters consisted of a tungsten or carbon-fiber core, coated with a dielectric material. Two coating materials were used: (1) Clark Electromedical Instruments Epoxylite resin and (2) Epidian 6 Epoxy resin (based on bisphenol A). Various properties of these emitters were measured, including the current-voltage characteristics, which are presented as Fowler-Nordheim plots, and the corresponding electron emission images. A field electron microscope with a tip (cathode) to screen (anode) distance of 10 mm was used to electrically characterize the emitters. Measurements were carried out under ultrahigh vacuum conditions with a base pressure of 10 -6 Pascal (10 -8 mbar).

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Section: Discussionsupporting

confidence: 90%

Epoxylite Influece on Field Electron Emission Properties of Tungsten and Carbon Fiber Tips

Alnawasreh

Al-Qudah

Madanat

et al. 2016

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“…Hence, the final layer thickness was about 150 to 200 nm. This was followed by baking the fiber emitter in an oven for 0.5 hour at 100°C, to remove the solvents, followed by 0.5 hour at 190°C to cure the resin, as described by Mousa & Kelly (2003).…”

Section: Methodsmentioning

confidence: 99%

“…Carbon fibers can emit stable currents for long periods of time under poor vacuum conditions, with greater resistance to ion bombardment than metal emitters possess. Coating carbon fibers with dielectric materials produces an increase in the emission current, improves its stability, and increases the emitter lifetime (Mousa & Kelly, 2003). This paper describes some new CFE experiments with coated carbon fibers.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Field Electron Emission from Dielectric Coated Highly Emissive Carbon Fibers

Almarsi

Hagmann

Mousa

2017

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This paper describes experiments aimed at characterizing the behavior of field electron emitters fabricated by coating carbon fibers with epoxylite resin. Polyacrylonitrile carbon fibers of type VPR-19, thermally treated at 2,800°C, were used. Each was initially prepared in a "uncoated" state, by standard electro polishing and cleaning techniques, and was then examined in a scanning electron microscope. The fiber was then baked overnight in a field electron microscope (FEM) vacuum chamber. Current-voltage characteristics and FEM images were recorded on the following day or later. The fiber was then removed from the FEM, coated with resin, "cured" by baking, and replaced in the FEM. After another overnight bake, the FEM characterization measurements were repeated. The coated fibers had significantly better performance than uncoated fibers. This confirms the results of earlier experiments, and is thought to be due in part to the formation of a conducting channel in the resin over layer. For the coated fiber, lower voltages were needed to obtain the same emission current. The coated fibers have current-voltage characteristics that show smoother trends, with greater stability and repeatability. No switch-on phenomena were observed. In addition, the emission images on the phosphor-coated FEM screen were more concentrated, and hence brighter.

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“…The fibre used was highly emissive polyacrylonitrile carbon fibre (PAN 1960) treated at 2800°C. A standard procedure, described in detail elsewhere, 13 was used to produce a coating of epoxy resin on the fibre; this procedure could be customized to yield the coating thickness of ¾0.2-0.3 µm that was found in our preliminary work to produce the most stable emission currents. High-resolution transmission electron microscopy (TEM), with a specially designed sample holder, was used to study the profile of the tips and the coatings.…”

Section: Methodsmentioning

confidence: 99%

“…13 The structure of the high-modulus carbon fibres used is explained elsewhere. 8,9,13 It seems that instabilities in the emission current from an uncoated emitter are associated with ion bombardment. The resin-coated tips are protected from direct ion bombardment, so the emission current is more stable.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of carbon‐fibre cold field emission tips with a dielectric coating

Mousa

Kelly²

2004

Surface & Interface Analysis

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Field electron emitters have been prepared by coating a carbon fibre with an epoxylite resin, and their properties investigated. The emission stability is improved compared with an uncoated fibre. An optimum coating thickness of 0.2-0.3 µm has been found. Energy spectra have been measured and peak shifts of up to 1 eV as a function of emission current have been observed. Surprisingly, these peaks shifts are comparable with those found for uncoated carbon fibres and for resin-coated tungsten emitters. Their origin is not clear, but it seems that resistive drop cannot be the whole explanation. We speculate that these peak shifts may be related to the dynamics of surface-state occupation at the material/vacuum interface.

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Stabilization of carbon-fiber cold field-emission cathodes with a dielectric coating

Cited by 19 publications

References 13 publications

Epoxylite Influece on Field Electron Emission Properties of Tungsten and Carbon Fiber Tips

Epoxylite Influece on Field Electron Emission Properties of Tungsten and Carbon Fiber Tips

Enhanced Field Electron Emission from Dielectric Coated Highly Emissive Carbon Fibers

Characteristics of carbon‐fibre cold field emission tips with a dielectric coating

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