微型热阴极性能及理论分析  

Performance and Theoretical Analysis of Miniature Thermionic Cathode

作　　者：张敏[1] 杨鹏云 张珂[1] 高玉娟[1] 孟维思 ZHANG Min;YANG Peng-yun;ZHANG Ke;GAO Yu-juan;MENG Wei-si(Beijing Vacuum Electronics Research Institute,Beijing 100015,China)

机构地区：[1]中国电子科技集团公司第十二研究所,北京100015

出　　处：《电子学报》2023年第6期1443-1447,共5页Acta Electronica Sinica

摘　　要：为了满足高频段真空器件对阴极提出大电流密度、小电子注尺寸的需求,本文利用聚焦离子束刻蚀技术在通过双离子束辅助沉积技术沉积了锆抑制膜的浸渍钪酸盐阴极表面上制备出发射面直径为100μm的微型阴极.实验结果显示:沉积的锆抑制膜在370 h内有效抑制了阴极的电子发射;当温度为950℃,其发射面的平均电流密度可达到43 A/cm^(2);当温度为1 000℃时,发射区域平均电流密度为58 A/cm^(2),但抑制区有了轻微发射.为了深入研究阴极微型发射区域的电子发射机理并揭示阴极抑制膜层抑制性能的原因,本文利用第一性原理建立了不同氧原子(O)吸附位以及不同钡原子(Ba)覆盖度的Ba-Sc-O-W原子结构模型和抑制膜层的Zr-Ba-Sc-O-W原子结构模型.研究发现:氧原子吸附的顶位Ba-Sc-O-W发射表面的功函数下降至1.497 eV,与钪酸盐阴极有效功函数为1.41 eV实验测试结果较为相近;随着温度的升高,阴极发射能力增强,但活性物质与Zr结合形成的Zr-Ba-Sc-O-W结构使抑制层抑制性能有所降低(Zr的功函数为4.05 eV,Zr-Ba-Sc-O-W计算所得功函数为3.348 eV).In order to meet the requirement of THz vacuum devices for high-current density and small-size electron beam,a kind of miniature thermionic cathode is prepared in this paper by depositing an anti-emission Zr coating on impreg⁃nated scandate cathode surface via dual ion-beam-assisted deposition(Dual IBAD)and then etching in the center of the antiemission coating a mini electron emission zone with a diameter of 100μm via focus ion beam(FIB).Experimental results show that the electron emission has been effectively suppressed in the anti-emission zone within 370 h,and that the average current density of the cathode reach 43 A/cm^(2) at 950℃and 58 A/cm2 at 1000℃.The Ba-Sc-O-W and Zr-Ba-Sc-O-W atomic structural models are established by employing ab initio density functional theory(DFT)calculation.It is found that the surface work function of Ba-Sc-O-W is 1.497 eV when O is absorbed at top site,closing to the experimental result(1.41 eV),and that the increase of working temperature contributed to the increase of cathode emission,whilst it also results in the formation of Zr-Ba-Sc-O-W atomic structure and the decrease of anti-emission performance(the work function of Zr and Zr-Ba-Sc-O-W are 4.05 eV and 3.348 eV respectively).

关 键 词：微型阴极 电子发射 电流密度 抑制膜 原子结构模型 

分 类 号：TN1[电子电信—物理电子学] O462.1[理学—电子物理学]