Ferroelectric plasma sources and their applications

Abstract

Summary form only given. Over the past decade intensive research in many laboratories was focused on the investigation of strong electron emission from ferroelectric samples. It was demonstrated that ferroelectric samples could emit electron current densities of hundreds of A/cm/sup 2/ with a repetition rate of several of MHz under the application of driving pulses with an amplitude of /spl sim/10/sup 3/ V. Two models were suggested to explain the observed electron emission. The first model is based on polarization reversal of the prepolarized ferroelectric sample which causes the appearance of noncompensated polarization charge and, consequently, large electric field on the surface of the ferroelectric. The second model suggests electron emission from the plasma which is created on the surface of the ferroelectric due to incomplete surface discharge. We present data which show the validity of the second model, namely that the source of electrons is the plasma. This plasma is formed by incomplete discharges on the surface of the ferroelectric sample within the first few nanoseconds of the driving pulse application. The parameters of the surface discharge plasma (plasma electron density and temperature, plasma expansion velocity, energy of plasma electrons and ions, and plasma uniformity) as well as the parameters of the neutral flow strongly depend on the polarization state of the ferroelectric material as well as on the parameters, and method of application of the driving pulse application. Data concerning the life-time of ferroelectric cathodes versus the driving pulse parameters are presented as well. We also describe the parameters of the electron beams generated in planar electron diodes with ferroelectric cathodes. It is shown that electron beam generation in a diode with a ferroelectric cathode is realized in the so-called plasma prefilled mode. Data are also presented concerning the uniformity of the extracted electron beam as well as the potential distribution in the diode.