An XPS and UPS Study on the Electronic Structure of ThOx (x 鈮?2) Thin Films

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• 作者：Pelin Cakir ; Rachel Eloirdi ; Frank Huber ; Rudy J. M. Konings ; Thomas Gouder
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：October 23, 2014
• 年：2014
• 卷：118
• 期：42
• 页码：24497-24503
• 全文大小：365K
• ISSN：1932-7455

文摘

Model systems are needed for surface corrosion studies of spent nuclear oxide fuels. For this purpose ThO₂ films have been prepared in situ by adsorption of molecular and atomic oxygen on Th metal films and by sputter deposition of Th metal in an Ar/O₂ gas mixture. Surface compositions and electronic structure were compared to the bulk oxide and oxygen substoichiometry effects investigated. X-ray and ultraviolet photoemission spectroscopy (XPS and UPS, respectively) were used to measure to Th-4f, O-1s core levels and the valence band region. The Th-4f line was analyzed in terms of the final-state screening model. The evolution of the binding energies with oxygen concentration has been studied. On Th metal, adsorption of molecular oxygen ceased after the formation of a ThO₂ surface layer. In the presence of atomic oxygen, the oxidation proceeded into the underlying bulk. The formation of oxygen interstitials was shown by the broadening of the O-2p and O-1s lines and by the increase of the O-1s/Th-4f ratio. Once ThO₂ is formed, all photoemission peaks from Th and O undergo a rigid shift to low binding energy.