Relationship between field emission property and composition of carbon nanotube paste for large area cold cathode J.Total energy distribution ͑TED͒ measurements were carried out for point electron sources operating in the cold field ͑T = 300 K͒ and Schottky ͑T = 1800 K͒ emission regimes. The full width at half maximum ͑FWHM͒ values of the TED's for both emission regimes were found to increase significantly above the respective theoretical values as the emitter radius ͑a͒ was decreased and as the angular current density ͑IЈ͒ was increased. This increase in the FWHM arises from the stochastic electron-electron interactions in the beam commonly known as the Boersch ͓Z. Phys. 139, 115 ͑1954͔͒ effect. A method was devised to extract the magnitude of the Boersch effect from the experimental TED's. The TED's were investigated as a function of IЈ and a. In addition, the reduced brightness for both emitters was calculated from the virtual source size and IЈ values as a function of the FWHM values.

Articles you may be interested inEnhanced field emission from lanthanum hexaboride coated multiwalled carbon nanotubes: Correlation with physical propertiesSingle crystal HfC was evaluated as a cold field emission ͑T = 300 K, Ͻ1 ϫ 10 −9 Torr͒ electron source for high-resolution scanning electron microscopy/transmission electron microscopy applications and it is shown to be an excellent candidate for this use. Single crystal HfC was produced and fabricated into a cold field emitter. Angular intensity and reduced brightness were determined from experimental I͑V͒ data. A software program was written to calculate from first principles the full width at half maximum of the emitted electron total energy distribution over a range of geometrical and tunneling parameters, including a component for space charge effects. Experimental energy distribution data are in good agreement with the modeling results. The reduced brightness, energy distribution, and emission stability of HfC are compared with commercially available sources. HfC produced a higher brightness and a lower energy spread than a W cold field source or a ZrO / W Schottky emitter. HfC maintains its emission level for 1 h in moderate UHV condition, which shows a dramatic improvement over the long-term stability of W. This stability combined with a durability that allows for frequent flash cleaning without degradation of the emitter end form makes HfC a highly promising cold field emission source.

Articles you may be interested inA compact ion source and accelerator based on a piezoelectric driver AIP Conf. Proc. 1525, 725 (2013); 10.1063/1.4802422 Development and characterization of an iodine field emission ion source for focused ion beam applications

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The authors report on electron emission defining and stability techniques use for specialized thermionic cathodes. Primarily lanthanum hexaboride and cerium hexaboride have been used for cathode materials but we also use hafnium carbide for cases where background atmospheres preclude the use of hexaborides. A common form of emission suppression is to embed an oriented single crystal in graphite to suppress side emission and to help shape the electric field. Single planar discs 50 lm in diameter have been tested for use as high brightness, stable, and long life thermal sources. Line sources have also been developed with linewidth/lengths to 10/500 lm. Emission tests performed have shown that long-term drift and short-term instabilities can originate from boride and carbon interactions respectively. Improved mounting techniques are shown to yield emission with short-term beam current stability <0.05%.