第一性原理研究掺入钒、锶的钡钨阴极表面功函数及吸附能  

First-Principles Study on the Surface Work Function and Adsorption Energy of Barium-Tungsten Cathode Doped with Vanadium and Strontium

作　　者：刘继琛 邵文生[1] 张珂[1] LIU Ji-chen;SHAO Wen-sheng;ZHANG Ke(The 12th Research Institute of China Electronics Technology Corporation,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7期1977-1982,共6页Acta Electronica Sinica

摘　　要：应用第一性原理赝势法,构建了不同的阴极表面原子模型,并计算了功函数和吸附能.以(2×2×1)W(001)面为基础,在表面的顶位、桥位和洞位分别吸附1 ML的O原子,发现O原子更倾向于吸附在顶位,并且功函数最大.将Ba原子吸附在W-O表面后,发现Ba原子更有可能吸附在洞位,表面最佳覆盖度在0.5 ML左右.在W-O-Ba表面的洞位吸附V原子和Sr原子,发现同时吸附2种原子后体系的吸附能更有可能取决于最后吸附的原子,V的吸附使表面功函数降低,Sr使表面功函数升高.最后制备了掺入3%钒酸锶的新型钡钨阴极,在1050℃下脉冲发射电流密度达8.71 A/cm^(2),高于普通铝酸盐钡钨阴极的6.77 A/cm^(2),通过实验证实理论仿真具有合理性,可以进一步优化表面结构,提高阴极发射能力.Using first-principles pseudopotentials,different atomic models of the cathode surface are constructed,and the work function and adsorption energy are calculated.Based on the(2×2×1)W(001)plane,1 ML of oxygen atoms are adsorbed on the top,bridge,and hole positions on the surface.It is found that O atoms are more inclined to be adsorbed at the top and have the largest work function.After adsorbing Ba atoms on the surface of W-O,it is found that Ba atoms are more likely to be adsorbed on the hole,and the best surface coverage is about 0.5 ML.V atoms and Sr atoms are adsorbed in the holes on the surface of W-O-Ba,and it is found that the adsorption energy of the system after the two atoms are ad⁃sorbed at the same time is more likely to depend on the last adsorbed atom.The adsorption of V makes the surface work function decrease,while Sr makes the surface work function increase.Finally,a new type of barium tungsten cathode doped with 3%strontium vanadate is prepared,and the pulse emission current density reaches 8.71 A/cm^(2) at 1050℃,which is higher than the 6.77 A/cm^(2) of ordinary barium aluminate cathode.The theoretical simulation results are verified to be rea⁃sonable by experiments,and it can further optimize the surface structure and improve the cathode emission performances.

关 键 词：第一性原理 钡钨阴极 功函数 吸附能 表面掺杂 

分 类 号：TN1[电子电信—物理电子学] O462[理学—电子物理学]