Low-voltage field emission from tungsten fiber arrays in a stabilized zirconia matrix

Field emitter array cathodes were fabricated from unidirectionally solidified composites of tungsten fibers in an insulating yttria-stabilized-zirconia (YSZ) matrix. A close-spaced molybdenum gate film (extractor) was formed utilizing e-beam evaporation of alumina as an insulator, which was overlayed by the molybdenum extractor. The high resistivity of the composite matrix coupled with the alumina insulator resulted in low leakage current and permitted dc operation of the device. Emission testing demonstrated current densities of 1--5 A/cm2 with leakage in the μA range for applied potentials of 125--200 V. Variation of emitter tip geometries from hemispheres to right circular cylinders to pointed cones produced increases in emission consistent with reduced tip radii