Atomic-Scale Picture of the Composition, Decay, and Oxidation of Two-Dimensional Radioactive Films

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• 作者：Alex Pronschinske ; Philipp Pedevilla ; Benjamin Coughlin ; Colin J. Murphy ; Felicia R. Lucci ; Matthew A. Payne ; Andrew J. Gellman ; Angelos Michaelides ; E. Charles H. Sykes
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：February 23, 2016
• 年：2016
• 卷：10
• 期：2
• 页码：2152-2158
• 全文大小：473K
• ISSN：1936-086X

文摘

Two-dimensional radioactive ¹²⁵I monolayers are a recent development that combines the fields of radiochemistry and nanoscience. These Au-supported monolayers show great promise for understanding the local interaction of radiation with 2D molecular layers, offer different directions for surface patterning, and enhance the emission of chemically and biologically relevant low-energy electrons. However, the elemental composition of these monolayers is in constant flux due to the nuclear transmutation of ¹²⁵I to ¹²⁵Te, and their precise composition and stability under ambient conditions has yet to be elucidated. Unlike I, which is stable and unreactive when bound to Au, the newly formed Te atoms would be expected to be more reactive. We have used electron emission and X-ray photoelectron spectroscopy (XPS) to quantify the emitted electron energies and to track the film composition in vacuum and the effect of exposure to ambient conditions. Our results reveal that the Auger electrons emitted during the ultrafast radioactive decay process have a kinetic energy corresponding to neutral Te. By combining XPS and scanning tunneling microscopy experiments with density functional theory, we are able to identify the reaction of newly formed Te to TeO₂ and its subsequent dimerization. The fact that the Te₂O₄ units stay intact during major lateral rearrangement of the monolayer illustrates their stability. These results provide an atomic-scale picture of the composition and mobility of surface species in a radioactive monolayer as well as an understanding of the stability of the films under ambient conditions, which is a critical aspect in their future applications.