HIGH-INTENSE PULSED ELECTRON EMISSION BY FAST POLARIZATION CHANGES IN FERROELECTRICS

The phenomenon of high-intensity pulsed electron emission from ferroelectrics, discovered at CERN in 1988, has attracted much interest and is today a subject of investigation all over the word. Applications of this new kind of electron source are manifold, since the emission effect does not rely on the quality of the vacuum, the electrons may have an initial kinetic energy up to several keV, the pulse duration can be varied, and the cross-section of the source may be determined from the electrode geometry. Thus, research and development on the Ferroelectric Electron Beam Source (FEBS) is wide-ranging and comprises pulse generation of femtosecond to microsecond duration, high current cathodes, large area emitters, micro sources, and electron emission from ferroelectric thin films. The phenomenon is initiated by suddenly unbalancing the charge equilibrium of the ferroelectric, and the emission of the pulsed electron beam is part of the relaxation process. A convenient method of achieving the initial perturbation is to change the spontaneous polarization by fast-rising electrical fields, which results in a (partial) polarization inversion or a transition from a non-polar to a ferroelectric phase. Here the mechanism is discussed, basic data of the FEBS are reviewed, switching and emitted charge from a PZT 55/45 are compared quantitatively, and finally an approach to an Integrated Ferroelectric Emissive Flat Panel Display is presented.