Dielectric-spontaneous polarization versus electron emission in perovskite cathodes

Strong electron emission in ferroelectric cathodes requires fast polarization change. We present the correlation between the emission of energetic electrons and the polarization change obtained experimentally. The shape of the emitted current pulse and its level depend on the amplitude and the rate of the polarization variation. The polarization variation showed a fast and a slow component, related to fast and slow nanodomain relaxation time respectively: The slow rate polarization of the relaxor samples used in our tests showed a relaxation time of a few microseconds. The emission in presence of the sole fast polarization naturally depends on the exciting pulse characteristics. The emission in presence of also the slow polarization depends strongly on the relaxation dynamics: The relatively long decay time leads to a freezing of screening electrons and consequently to a low emission level.