镧钼热阴极表面活性层中的镧超微粒子  

Lanthanum Ultra-Fine Particles of La_2O_3-Mo Thermionic Cathode Surface Active Layer

作　　者：郝世明[1] 聂祚仁[2] 

机构地区：[1]河南科技大学理学院,河南洛阳471003 [2]北京工业大学材料科学与工程学院,北京100022

出　　处：《中国稀土学报》2009年第1期161-164,共4页Journal of the Chinese Society of Rare Earths

基　　金：国家863项目(2002AA322010);河南科技大学人才科学研究基金(05-079)资助项目

摘　　要：为了研究镧钼阴极表面发射机制,利用新型阴极研究装置研究阴极发射性能与表面元素La,O比例的关系,发现表面层中La/O比例越高,阴极的发射性能越好。在实验基础上提出了金属La超微粒子埋藏于La2O3晶体中的热阴极表面发射模型,模型认为活性层中的超额镧以镧超微粒子形式存在,La超微粒子中的电子在热激发下越过肖特基势垒进入La2O3晶体的导带进而克服表面电子亲和势逸出到真空,提供了电子发射的丰富源泉。由于肖特基势垒远小于La2O3的禁带宽度,并且超微粒子可以使耗尽层厚度变薄,极大降低了电子发射到真空的阈值。To study the surface emission mechanism of La2O3-Mo cathode, we investigated the relation between cathode surface atomic La/O ratio and cathode emission property by a new set of cathode research instrument. It was found that the cathode emission properties were affected intensively by the surface atomic La/O ratio, the higher the La/O ratio, the better the emission property. According to the experiment results, we proposed the following cathode surface emission model in which La ultra-fine particles buried in the insulator （ La2O3 ） matrices. The excess lanthanum existing in the ultra-fine particles provided a source of electrons, which could be thermally exited into conduction band of La2O3 across the Schottky bartier. These electrons located in the conduction band of La2O3 had only to surmount the surface barrier （ electron affinity EA ） of the La2O3, in order to escape into vacuum. Since the Schottky barrier was smaller than the bandgap Es of La2O3, and La ultra-fine particles could narrow the thickness of depletion layer, the threshold of electron emission into the vacuum was reduced.

关 键 词：热阴极 发射机制 发射模型 超微粒子 稀土 

分 类 号：TG146[一般工业技术—材料科学与工程] TG422[金属学及工艺—金属材料]