E.P. Sheshin

Influence of the interelectrode distance in electrophoretic cold cathode fabrication on the emission uniformity

Abstract In the present work, we studied the influence of the distance between electrodes in the electrophoretic process of flat cold cathode fabrication on the uniformity of the emission centers distribution. As the emitting material, we used single-wall carbon nanotubes. We found that the uniformity of field emission strongly depends on the distance between electrodes during the electrophoretic deposition. The best results have been achieved when the distance was smallest within the limits of the studied range (0.3–1.8xa0cm). For the high distances (1.1–1.8xa0cm), most of the emission sites were located on the edges of the cathodes. Good uniformity of field emission current has been achieved for the cathodes deposited with interelectrode distance equal to 0.3xa0cm. The cathodes were tested in the diode construction with the cathode–anode gap of 200xa0μm. Uniform light emission was obtained after the short training in the vacuum chamber. The turn-on voltage was 600xa0V, and the maximum achieved current was 850xa0μA at an applied voltage of 1.3xa0kV.

Electron gun with field emission cathode of carbon fiber bundle

The electron gun with field emission cathode is developed. The cathode was made of a bundle of carbon fibers. Specific properties of electron gun with bundles of carbon fibers are related to mechanical displacement of carbon fibers in the bundle. Specific types of emission current instability in connection with mechanical properties of cathode are described. The developed electron gun could be used to replace hot cathodes. Application of the gun for a light source and compact x-ray tube is considered.

Properties of carbon materials, especially fibers, for field emitter applications

An overview of different carbon materials (except carbon nanotubes (CNT)) applicable for production of field emission cathodes (FECs) is given. A classification of carbon materials is proposed, which simplifies the choice of carbon material suitable for specific field emission applications. Field emitters from carbon fibers, carbon composites and massive carbon are considered in more detail. Training techniques improving the emission current stability are described. Such training is suitable for a variety of different carbon-based cathodes.

Characterizations of light sources with carbon fiber cathodes

Abstract In the present work a cathodo-luminescent lamp with a polyacrylonitrile carbon fiber bundle cathode is presented. Electrical and spectral-brightness characteristics of the designed prototype are analyzed. The optimal anode voltage is 10xa0kV and the anode current is 150xa0μA. For this electrical regime the brightness of this light source is up to 13,000xa0cd/m2 (for the green phosphor) at the light efficiency about 7xa0lm/W. The low light efficiency is explained by technological aspects of phosphor coating.

Calculation of the thicknesses and elastic properties of thin-film coatings using atomic-force acoustic microscopy data

The feasibility of applying atomic-force acoustic microscopy to measure the elastic properties of thin-film coatings and their thickness in the range from several to several hundreds of nanometers is studied. In practice, this technique can be used to study diamond-like coatings. The key point of our method is application of “flat” tips, which provide a constant tip-surface contact area and, hence, a constant contact stiffness. The reason for using such tips is that experimental data for thin-film structures gained with standard (rounded) tips cannot be given an adequate quantitative interpretation. Numerical simulation is used to evaluate the thickness and indentation modulus of a coating from contact stiffness kcont measured by atomic-force acoustic microscopy.

Doping of graphite by an alkaline-earth metal to reduce the work function

A technique for reducing the work function of a field-emission graphite cathode by doping it by an alkaline-earth metal (barium) is suggested. A model of formation of a barium monolayer on the cathode surface is proposed. Field-emission tests show that the operating voltage of the doped cathode is lower than that of the undoped one with the same emission current.

Prediction of field emitter cathode lifetime based on measurement of I–V curves☆

Abstract A technique is presented, which allows the prediction of field emitter cathode lifetime without long-term direct measurements of cathode parameters stability. This technique is based on periodic measurements of cathode I – V characteristics. Moreover, it allows performing a post-experiment optimization for the appropriate choice of the feedback system to provide a stable operation during a long time. The proposed technique was applied to study the emission properties of reticulated vitreous carbon (RVC) and thermo-enlarged graphite (TEG). For the given cathodes, the characteristic time of the cathode destruction was estimated.

Application of holographic diffusers to improve light uniformity of source with carbon fiber cathodes

Numerous advantages of field emission cathodes of carbon materials such as reliability, high efficiency, long lifetime, and short switching time make them great candidates for vacuum electronics applications such as light sources, LCD backlights, and many others. However, because of field emission features of carbon emitters there exists an unevenness of light distribution on the phosphor screen in cathodoluminescent light sources. One of the methods of improving the light uniformity is the application of holographic light shaping diffusers. In the present work we have investigated a possibility to improve a brightness distribution in the cathodoluminescent light source with a carbon fiber cathode applying various holographic diffusers.

Simulation of contact stiffness of a hemispherical island inclusion

Numerical analysis is carried out for constructing a model simulating the contact stiffness of a solitary hemispherical island inclusion in an infinitely extended substrate. The contact stiffness is measured using atomic force acoustic microscopy with tips having a constant contact radius. Finite element analysis using the isotropic model of the materials is employed for this purpose. The model can be used for studying nanocomposite materials.

Effect of interference on field electron emission

Carbon nanotubes are studied with the help of an electron projector and dispersion field-emitted energy analyzer. Probe current-voltage characteristics of two samples exhibited wave-like modulation caused by periodic variations in field-emitted electron energy spectra observed with increasing emission voltage. Deviations of the current from the average Fowler-Nordheim line were up to ±35% within one period. The explanation relies on the model of Young’s interference from two coherent sources.