Stable, High Density Field Emission Cold Cathode

Abstract

The practical application of the field emission electron source has heretofore been impeded by insufficient reliability. Instability (i.e., changes in emitted current at a fixed applied voltage) results from changes in the cold cathode surface associated with contamination and sputtering. The cold clean cathode is shown to be electrically stable at dc emission densities up to 107 amp/cm2. Techniques are discussed which permitted stable operation of a single needle tungsten cathode during 1000 hr at an average beam power of 35 w (corresponding to a beam power density of 35 billion w per unit cathode area). A simple method is described which permits reconditioning of the cathode surface when required, and apparently extends life indefinitely; operating periods in excess of 12 000 hr are reported. An explanation is suggested for the small, gradual residual changes observed in the emitted current.

Arcing and voltage breakdown in vacuum microelectronics microwave devices using field emitter arrays: Causes, possible solutions, and recent progress

“…In the 1950s, motivated by a desire to develop useful field emission devices ͑particularly microwave͒ Dyke and co-workers started extensive investigations of high current dc and pulsed FE. Dyke verified the Fowler-Nordheim ͑FN͒ theory over a wide range of currents, 1 identified and quantified the upper limit to dc or pulsed FE current, 2 determined the emitter processing and environmental requirements for long duration, moderately stable FE from cold or heated tungsten, 3,4 and built a variety of experimental devices, particularly cathode ray tubes ͑CRTs͒ and microwave tubes at 10 GHz. 5,6 Dyke recognized that single tips could only produce limited beam conductance, hence microwave applications would require field emitter arrays ͑FEAs͒ with uniform tip radii.…”

Atomic-Resolution STEM at Low Primary Energies

“…The time over which the emission current decays to one half of the starting value is usually denoted by t 1/2 . In actual electron guns, t 1/2 varies widely, from less than a minute to several hours or even several days (Martin et al 1960).…”

Accurate Determination and Measurement Error of Pretilt Angle in Liquid Crystal Cell

“…Apparently the current fluctuates about a fixed value even for an extended period of several hours. The emission behaviour of a clean tungsten tip is rather different: After a rapid decrease of the current down to 10-20% of its initial value, this reduced level is maintained for a long time until an uncontrollable increase occurs caused by a roughening of the surface, which finally destroys the tip (Martin et al 1960). The reason for this difference might be that the surface of the metallic glass tip was at no time completely clean but was still covered with adsorbates.…”