铁电体阴极的实验研究

EXPERIMENTAL STUDIES OF FERROELECTRIC CATHODES

铁电体阴极是一种具有很大发展潜力的新型高亮度、高重复率、强流电子束源。电子发射的基本机制是利用铁电体中的快极化反转产生的极化值变化,其转换时间为纳秒量级,因此,重复率可达数百兆赫;最大电子发射密度为10^(14)/cm^2;发射电流的大小取决于样品上激励电压的上升时间;发射电子的最大能量决定于样品厚度,初步估算,在电流强度相同的情况下,铁电阴极的亮度可比激光照射的光阴极高4倍,与传统电子源相比,它具备许多特殊的优点,本文报导了E∥P和E⊥P两种实验模式,测得的最大发射电流密度分别为12A/cm^2和21A/cm^2。

Electron emission produced by fast polarization change of the ferroelectrics is a potential electron beam source. Both experimental modse, E∥P and E⊥P, as well as their behaviors are reported in this paper. J - E characteristics of both materials, PZT - 95/ 5 and PLZT -1/ 95/ 5, for different modes are given. It's pointed out that the presence of the metal strip grid is a disfavour factor, which results in redistribution of the current between the anode and the strip grid electrode. Moreover, the limited breakdown threshold of the sample is a main hinder for increasing excitation field. In order to overcome these difficults, a mode, E⊥ P, has been developed using 'polarization rotation' idea to replace 'polarization reversion' . This idea has been confirmed by our experiments.