We report on fabrication, performance and modeling of field emission c
athodes made from refractory transition metal carbides. The primary ca
rbides under study include HfC, TaC, and ZrC. Single crystal carbide s
pecimens were prepared by arc floating zone refinement from sintered s
tock. Emission patterns are shown along with emission stability data.
Work function ordering of various crystal planes determined by means o
f field emission microscopy is reported and comparisons are made with
results from thermionic projection microscopy. Typically, the carbides
show that phi210,310 < phi100 almost-equal-to phi110 >> phi111. Resul
ts of effective thermionic work function measurements are presented fo
r macroscopic clean crystal surfaces. An emission increase mode is des
cribed wherein applied tip voltages can be decreased by half, while si
multaneous emission current increases of a thousand-fold are observed.
Stable currents of 0.5 mA DC and lifetimes > 2400 h are reported. Sta
ble pulsed field emission of > 10 mA for a single emitter at pulse len
gths of 10 mus and duty factors of 0.01-0.001 are reported. Single-pul
se currents as high as 48 mA were observed from a single emitter tip.
Current densities have been calculated to be in the high 10(8) A/cm2 r
ange.