A model study of the role of workfunction variations in cold field emission from microstructures with inclusion of field enhancements

Abstract

An analytical study of field emission from microstructures is presented that includes positiondependent electric field enhancements, quantum corrections due to electron confinement and fluctuations of the workfunction. Our calculations, applied to a ridge microstructure, predict strong field enhancements. Though quantization lowers current densities as compared to the traditional Fowler-Nordheim process, strong field emission currents can nonetheless be expected for large emitter aspect ratios. Workfunction variations arising from changes in electric field penetration at the surface, or due to interface defects or localized screening, are shown to be important in enhancing the emission currents.

Comparison between Single-Walled CNT, Multi-Walled CNT, and Carbon Nanotube-Fiber Pyrograf III

“…where ߛ is the phenomenological field enhancement factor, and ‫ܭ‬ is the slope of FN plot, the value of ߛ for CNTFs will be higher than SWCNTs and MWCNTs, so that will explain the value of VTH for the three type of the emitter [18,19]. Figure 9 shows the emission image at VSW for the second set of the emitter.…”

“…Fundamentally, the field emission phenomena are highly non-equilibrium quantum mechanical processes that require the precise description of electronic structures of the nanotubes, and the equation of FN still in development to fully describe the electron emission from single-walled carbon nanotubes. From the result we can say that the SWCNTs and CNTFs have approximately similar behavior, while SWCNTs emission current turned on earlier, and that referring to the smaller radius of the nanotubes, but there are other influences on this matter, like the effect of the enhancement factor and field penetration, which the electric field can penetrate to CNTs to suppress the charge potential near the tip of tube and induce a few extra electrons [13], and the effective work function where its affected by the penetration of the electric field [18]. The cleanness the Carbon Nanotubes (CNT) surface effects on the current fluctuation, which is can be achieved by wet chemical cleaning and thermal post-treatment [19].…”

A study of DC electrical breakdown in liquid helium through analysis of the empirical breakdown field distributions

“…30 Moreover, just as the local microscopic field on the surface of the electrode can be significantly different than that of the applied macroscopic field as a result of micro-protrusions that vary in both size and shape on the surface, the work function is not necessarily uniform and constant across the electrode surface or with the externally applied field. 31 For fields of 10 8 V/cm or greater, work function changes above 0.5 eV are possible. 32…”

Heating based model analysis for explosive emission initiation at metal cathodes

“…For a protruding ridge as may likely exist on the surface of an emitting cathode, the field enhancement factor can easily be obtained through conformal mapping techniques. 22,23 Details have been discussed by our group 24,25 and field enhancements by factors in excess of 10 3 shown to result for an emitter height of 10 µm and a 20 nm width. Furthermore, the presence of an ion (whether due to a separate material ejection and its subsequent ionization, or in the plasma surrounding the cathode), would alter the surface electric fields and lower the barrier for electron tunneling.…”