1. A new attempt to further reduce the work function of the cesiated surface: The strongest electronegative element fluorine co-adsorption with cesium on Mo (001) surface
- Author
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Heng Li, Xin Zhang, Yuhong Xu, Guangjiu Lei, Sanqiu Liu, Zilin Cui, Jun Hu, Yiqin Zhu, Xiaolong Li, Xiaoqiao Liu, Huaqing Zheng, Shaofei Geng, Xiaochang Chen, Haifeng Liu, Xianqu Wang, Hai Liu, and Changjian Tang
- Subjects
Cesiated surface ,Fluorine ,Work function ,Negative ion source ,Dipole moment ,Nuclear engineering. Atomic power ,TK9001-9401 - Abstract
The efficiency of hydrogen negative ion production in negative ion sources depends on the work function of the molybdenum surface. Deposition of cesium (Cs) atoms on the Mo surface reduces the work function from over 4.0 eV to about 1.50–1.80 eV. However, the Fermi level remains below the affinity level (−0.75 eV) of hydrogen negative ions. To explore further reduction methods, the work function of Cs co-adsorbed with fluorine on the Mo (001) surface was studied using DFT calculations. The results show that at 4/16 θ Cs coverage, adding fluorine can reduce the work function, achieving the lowest value of 1.40 eV at 8/16 θ F coverage. Analysis reveals a significant vacuum-inward dipole moment with fluorine-Cs co-adsorption, favorably reducing the work function. However, fluorine’s strong electronegativity also creates a surface-directed dipole moment, increasing the work function. Introducing fluorine is beneficial only at 4/16 θ Cs coverage, indicating that precise control of Cs coverage is necessary to achieve lower work functions.
- Published
- 2024
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