XPS/AES研究室温下铀基氮化层的表面氧化

采用俄歇电子能谱仪（AES）以及X射线电子能谱仪（XPS）原位研究了室温下铀基氮化层在纯O₂气氛中的初始氧化过程。原位氧化过程中U的AES微分谱以及U 4f、N 1s、O 1s谱的变化显示，U₂N_3+x氧化形成了UN_xO_y；AES深度剖析结果显示，经18 L以及120 L O₂曝露氧化层与氮化层界面处均出现N的富集，表面形成氧化层-富氮层-氮化层的三明治结构。富氮层U原子的AES微分谱中OPV混合峰的峰位远低于氮化层与氧化层，N 1s谱向低能侧移动, 表明富氮层主要成分为N/U比较氮化层更高的氮化物。推测U₂N_3+x的氧化基于O原子对N原子的置换，被置换出的N原子进入邻近晶格使N/U比增大并阻碍O原子向内的进一步扩散。

Investigation of Surface Oxidation of Nitride Layer on Uranium by In-situ XPS and AES Technique

The initial oxidation behavior of nitride layer (U₂N_3+x) on uranium metal was investigated by in-situ X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) in oxygen atmosphere at room temperature. AES differential spectrum of uranium and U 4f, N 1s, O 1s spectra all show that UN_xO_y is formed during the oxidation of nitride layer. When exposuring to 18 L and 120 L oxygen it was observed by AES profile measurements that an oxide-nitrogen rich-nitride sandwich structure was formed on the surface of nitride layer. As the OPV mixing peak of nitrogen-rich film is much lower than that of the nitride and oxide layer, and N 1s peak shows the same trend as OPV peak, nitrides with higher N/U ratio may form in the nitrogen-rich layer. It is implied that during the oxidation of uranium sesiquinitride the N atom will be substituted by O atom and move to fill the vacancies of neighbor nitride crystal lattice, which increases the N/U ratio of neighbor field and prevents the O atom’s diffusion.