Characteristics of ferroelectric electron emission

Summary form only given. The application of ferroelectric ceramics for electron beam generation is being studied at a number of research institutions and current densities /spl sim/100 A/cm/sup 2/ have been reported. Such ferroelectric materials can exhibit a spontaneous polarization, P/sub s/, of up to 100 /spl mu/C/cm/sup 2/. Emission occurs when the equilibrium state of the ferroelectric is changed rapidly by applying a pulsed electric field and a fraction of the surface screening charge is released at a gridded electrode. The majority of these studies are conducted with poled ceramics oriented such that the negative screening charge is facing the A-K gap. We report results which suggest that emission characteristics are not dependent on sample orientation. Studies conducted with a variety of gridded electrode geometries offer insights into the mechanism that initiates electron emission. Previously reported studies at Cornell showed that /spl sim/60eV electrons were observed to cross A-K gaps of /spl les/0.5 cm when the ferroelectric cathode was switched with a 200 ns pulse at voltages /spl les/2 kV. Recent measurements reveal a dramatic difference in electron energy when the polarity of the switching voltage is changed. With a 2 cm A-K gap and a +1.8 kV, 200 ns switching pulse, electron energies measure /spl sim/ 100 eV, but a switching pulse of -1.8 kV produces electrons with energies of /spl sim/600 eV.