物理学报2018，Vol.67Issue(2)：213-223,11.DOI:10.7498/aps.67.20172055
沉积态铀薄膜表面氧化的X射线光电子能谱
Surface oxidation of as-deposit uranium film characterized by X-ray photoelectron spectroscopy
摘要
Abstract
Uranium film is a main functional component to realize the high efficiency conversion of laser to X-ray in the study on laser inertial confinement fusion. It also has important applications in relevant physics experiments. Due to its active chemical properties, the metal uranium film is extremely difficult to preserve in the atmosphere. A variety of methods may help to avoid the oxidation of uranium film,such as coating protective layer,vacuum or inert atmosphere protection. But under these conditions,the oxidation property of uranium film still needs experimental investigation. In this paper, the oxidation processes of uranium films under different atmospheres are studied by X-ray photoelectron spectroscopy (XPS)and depth profiling. Firstly,uranium films and gold-uranium multilayer films are prepared by ultra-high vacuum magnetron sputtering deposition, and then they are exposed to atmosphere, high purity argon and ultrahigh vacuum for a period of time. Finally, the distributions and valence states of oxygen and uranium elements are investigated by XPS depth profiling. The oxidation mechanism is analyzed according to the oxidation products and the microstructure characteristics of samples. The results show that the oxygen element is undetectable in the initial films. In the Au-U multilayer film, the protective ability of Au layer is greatly weakened by the micro-defects. The defect is not only the micro channel of oxygen entering into the sample directly, but also the origin of the interlaminar cracks at the Au/U interface. In about three weeks,the uranium layer is severely oxidized and large area lamination occurs. The oxidation products consist of a dense oxide thin film on uranium surface and corrosion pitting around the defects,which are mainly UO2. For the pure uranium film, the surface of the film is completely oxidized when it is exposed to high purity argon only for 6 h. The UO2layers with different thickness values are formed on their surface, which is due to the rapid diffusion of oxygen atoms at the columnar grain boundaries of the film. After the sample is exposed to the ultra-high vacuum for 12 h,UO2layer with a thickness of less than 1 nm is generated on the surface of the pure uranium film. In the etching of oxide by argon ion beams, the preferential sputtering effect of O is produced, and UO2is reduced into non-stoichiometric UO2?x. The effect of preferential sputtering is weakened with the decrease of oxide content. When the oxide content is less than 10%,the reduction of UO2can hardly be detected.关键词
沉积态/铀薄膜/氧化/X射线光电子能谱Key words
deposition/uranium film/oxidation/X-ray photoelectron spectroscopy引用本文复制引用
杨蒙生,邢丕峰,易泰民,郑凤成,唐永建,张林,杜凯,李宁,赵利平,柯博..沉积态铀薄膜表面氧化的X射线光电子能谱[J].物理学报,2018,67(2):213-223,11.基金项目
国家自然科学基金(批准号:51702303)资助的课题. Project supported by the National Natural Science Foundation of China (Grant No. 51702303). （批准号:51702303）
