El Jamal Ghada, Gouder Thomas, Eloirdi Rachel, Jonsson Mats
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Department of Chemistry, Applied Physical Chemistry, Sweden.
Dalton Trans. 2021 Jan 19;50(2):729-738. doi: 10.1039/d0dt03562a.
Thin films of UO2, U2O5, and UO3 were prepared in situ and exposed to reactive gas plasmas of O2, H2 and H2O vapour produced with an ECR plasma source (electron cyclotron resonance) under UHV conditions. The plasma constituents were analysed using a residual gas analyser mass spectrometer. For comparison, the thin films were also exposed to the plasma precursor gases under comparable conditions. Surface analysis was conducted using X-Ray and ultraviolet photoelectron spectroscopy before and after exposure, by measuring the U 4f, O 1s core levels and the valence band region. The evolution of the peaks was monitored as a function of temperature and time of exposure. After interacting with water plasma at 400 °C, the surface of UO2 was oxidized to a higher oxidation state compared to when starting with U2O5 while the UO3 film displayed weak surface reduction. When exposed to water plasma at ambient temperature, the outermost surface layer is composed of hexavalent uranium in all three cases.
二氧化铀（UO₂）、五氧化二铀（U₂O₅）和三氧化铀（UO₃）薄膜在超高真空（UHV）条件下原位制备，并暴露于由电子回旋共振（ECR）等离子体源产生的氧气（O₂）、氢气（H₂）和水蒸气（H₂O）的反应性气体等离子体中。使用残余气体分析仪质谱仪分析等离子体成分。为作比较，这些薄膜在类似条件下也暴露于等离子体前驱体气体中。在暴露前后，通过测量U 4f、O 1s 芯能级和价带区域，使用X射线和紫外光电子能谱进行表面分析。监测峰的演变作为暴露温度和时间的函数。在400℃与水等离子体相互作用后，与以U₂O₅开始时相比，UO₂的表面被氧化到更高的氧化态，而UO₃薄膜显示出微弱的表面还原。当在环境温度下暴露于水等离子体时，在所有三种情况下，最外层表面层均由六价铀组成。
