Features and technology of ferroelectric electron emission

Abstract

Spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a non-polar state or vice versa. If spontaneous polarization changes are induced at a submicrosecond time-scale, strong uncompensated surface charge densities and related fields are generated, which may lead to the intense self-emission of electrons from the negatively-charged free surface areas of the ferroelectric cathode. The nature of this self-emission differs essentially from other methods of ferroelectric electron emission and from conventional electron emission in that the latter methods are only achieved by extracting electrons with externally applied electric fields. When electron guns are constructed with ferroelectric cathodes, new design criteria have to be taken into account. The intensity, the energy, the temporal and spatial distribution and the repetition rate of the emitted electron beams can be adjusted within wide limits. The advantages of ferroelectric cathodes and the technological difficulties arising during their production, preparation, and operation are identified and discussed and solutions to the problems are proposed. Experiences with a few applications of ferroelectric electron emission are reported and suggestions for further applications are made.

Photochemistry on a polarisable semi-conductor: what do we understand today?

“…The interactions between dipoles in unit cells cause polarisation alignment resulting in a polarisation bound charge at the surface of the block of ceramic. This polarisation charge affects surface topography, chemical reactivity, optical and electronic properties of ferroelectric surfaces and interfaces, and this is clearly demonstrated by phenomena such as ferroelectric electron emission [58,59], polarisation dependent work function [60], metal photodeposition [32,61].…”

Neutralization principles for the extraction and transport of ion beams

“…The exit hole and neutralization channel radius is determined uniquely by the electron beam emittance e , velocity v e (energy), and current I and can be calculated with Eq. (15). By combining Eqs.…”

“…The additional non-neutralized part of the ion beam undergoes the same phase-space blow-up as a classically extracted ion beam. Equations (13)(14)(15) describe the end phase of full ion beam neutralization. The transition from the original state of non-neutralized ion and electron beams, where the condition in Eq.…”

“…Ferroelectricallygenerated pulsed hollow electron beam pulses [15] of about 50 ns FWHM length, with kinetic energies of a few keV, with 1 to 5 A current amplitude and 10 to 30 A/cm 2 current density [16,17] were sent in the opposite direction through the extraction gap into the source equipped with an Al target. When simply neutralizing the Langmuir-Child current density of Al 1+ or Al 2+ ions, the totally extracted current density measured immediately after the neutralization section was equal to 2 ×j LC , in accordance with the Langmuir-Child law.…”

Ceramic disks as efficient and robust cathodes

“…The emission presented in the paper refers to energetic electrons expelled in a ceramic disk when excited by a fast high voltage pulse applied to the electrodes deposited on the two surfaces [1,2]. The so-called relaxors and antiferroelectric ceramics with fast transition under the action of an electric field are suitable for electron emission [3].…”