XPS/AES研究室温下铀基氮化层的表面氧化

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

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,U2N3+x氧化形成了UNxOy;AES深度剖析结果显示,经18L以及120LO2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U2N3+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。

The initial oxidation behavior of nitride layer（U2N3＋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 UNxOy 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.